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Self-similar evolution in nonlocal nonlinear media

Theodoros Horikis, Dimitri Frantzeskakis, Nalan Antar, Ilkay Bakirtas, and Noel Smyth

Doc ID: 362010 Received 08 Mar 2019; Accepted 24 Jun 2019; Posted 24 Jun 2019  View: PDF

Abstract: The self-similar propagation of optical beams in a broad class of nonlocal, nonlinear optical media is studied utilizing a generic system of coupled equations with linear gain. This system describes, for instance, such propagation in nematic liquid crystals and optical thermal media. It is found, both numerically and analytically, that the nonlocal response has a focusing effect on the beam, concentrating its power around its center during propagation. In particular, the beam narrows in width and grows in amplitude faster than in local media, with the resulting beam shape being parabolic. Finally, a general initial localized beam evolves to a common shape.

Tm3+/Yb3+: BaMoO4 phosphor for high-performance thermometry operating in the first biological window

Xin Liu, Ruoshan Lei, Yin Li, and Shiqing Xu

Doc ID: 365688 Received 22 Apr 2019; Accepted 23 Jun 2019; Posted 24 Jun 2019  View: PDF

Abstract: The development of optical thermometers operating within the first biological window (650-1000 nm) has drawn great interest lately. Here, a new type of luminescent thermometer relying on the intensity ratio between 1G4-3F4 (652 nm) and 3F2,3-3H6 (691 nm) transitions in Tm3+/Yb3+: BaMoO4 phosphor is reported under 980 nm excitation. The thermometry is found to be independent on the excitation power, benefiting the reduction of measurement error. Moreover, it exhibits extremely high absolute sensitivity ranging from 210.5×10-4 to 1034.5×10-4 K-1 in 298-498 K. The maximal relative sensitivity and temperature resolution (1.36%K-1 and 0.37 K, respectively) are also among the highest values of those previous thermometric materials. Therefore, the Tm3+/Yb3+: BaMoO4 phosphor is a promising candidate for temperature sensors with high performance.

Photopolymer based coaxial holographic lens for spectral confocal displacement and morphology measurement

Hongpeng Liu, wang baohua, wang rui, WANG MingChang, Yu Dan, and Wang weibo

Doc ID: 365910 Received 25 Apr 2019; Accepted 22 Jun 2019; Posted 24 Jun 2019  View: PDF

Abstract: Spectral confocal displacement and morphology measurement device using photopolymer based coaxial holographic lens as a high dispersion element is developed. Linear dependence of axial spatial position on peak wavelength of dispersion spectrum provides a high accuracy and large range for measuring displacement and morphology. In the linear dispersion region, accompanying with 120nm shift of peak wavelength the measureable position range exceeds 20mm. The experimental available accuracy of displacement and morphology can reach 47.5μm/0.5nm using commercial optical fiber spectrum with a resolution of 0.5nm. Utilizing ultra-thin polymer based holographic lens with high dispersion can effectively compact the device size. Simultaneously, it can provide a large axial dispersion for measuring the spatial position characterization compared with the traditional glass based dispersion lens group. Holographic optical lens based on photopolymer is expected to apply in high-precision surface topography measurement of large-scale macroscopic objects. It will improve the measurement accuracy and accelerate the development of holographic optical elements

A novel high-resolution few-pattern method for 3D optical measurement

Gaoxu Wu, Yanxue Wu, Lingchi Li, and Fei Liu

Doc ID: 361504 Received 05 Mar 2019; Accepted 22 Jun 2019; Posted 24 Jun 2019  View: PDF

Abstract: Accurately and fast obtaining the three-dimensional (3D)shape information of objects becomes increasinglyimportant in various scientific fields. However,simultaneously achieving the high-resolution and high-speed 3D shape measurement of unknown objectsremains challenging in practical. In this letter, wepropose a novel variant shifting-phase method for 3Doptical measurement. Based on digital fringe projection(DFP) system, the method performs a point-wise high-resolution measurement of objects by projecting onlyfour intensity-coded patterns. We can retrieve thewrapped phases and their corresponding fringe orderssimultaneously from these four patters, and do notrequire any pre-acquired information of the object.Experiment results successfully demonstrate theeffectiveness of the easy-to-operate method.

Broadband extreme ultraviolet dispersionmeasurements using a high-harmonic source

Matthijs Jansen, Xiaomeng Liu, Kjeld Eikema, and Stefan Witte

Doc ID: 368179 Received 22 May 2019; Accepted 21 Jun 2019; Posted 24 Jun 2019  View: PDF

Abstract: We demonstrate direct dispersion measurements of various thin films at extreme ultraviolet (EUV) wavelengths, using a table-top laser-driven high-harmonic generation (HHG) source. In this method, spatially separated identical EUV pulses are generated through HHG with a pair of phase-locked infrared pulses. The EUV pulses are re-imaged to a sample plane using a single toroidal mirror, such that one pulse illuminates the target thin film while the other pulse passes through a reference aperture. By comparing the EUV interference with and without sample, we are able to extract the dispersion properties of the sample, integrated over the full film thickness. We have measured thin films of titanium, nickel, copper and silicon nitride, demonstrating that this technique can be applied to a wide range of materials, only requiring a film thin enough for sufficient EUV transmission.

Abruptly autofocusing beams from phase perturbations having forced symmetry

Dafne Amaya, Oscar Martinez Matos, and Pablo Vaveliuk

Doc ID: 368576 Received 27 May 2019; Accepted 21 Jun 2019; Posted 24 Jun 2019  View: PDF

Abstract: A controllable manipulation of the energy distribution of caustic beams possessing rectangular symmetry is presented. The beams are designed from the spectral phase by adding a linear and/or quadratic perturbation having forced symmetry. This approach breaks the overall caustic structure into branches allowing a fully controllable displacement of each branch. The caustic breaking leads to peculiar propagation configurations for rectangular beams. Among them, we highlight the abruptly autofocusing beam which until now was exclusively associated to caustic beams with circular symmetry. Thereby, the abruptly autofocusing effect can be yielded for one dimensional light sheets contrary to what happens for circularly symmetric beams. The theoretical predictions are supported by experiments. Besides, the focus width of such rectangular beams can be reduced beyond the standard diffraction limit.

Beam Profiler Network (BPNet)- A Deep Learning Approach to Mode Demultiplexing of Laguerre-Gaussian Optical Beams

Barak Hadad, Alon Bahabad, Amit Bekerman, and Sahar Froim

Doc ID: 368961 Received 30 May 2019; Accepted 21 Jun 2019; Posted 24 Jun 2019  View: PDF

Abstract: The transverse field profile of light is being recognized as a resource for classical and quantum communications for which reliable methods of sorting or demultiplexing spatial optical modes are required. Here, we demonstrate, experimentally, state-of-the-art mode demultiplexing of Laguerre-Gaussian beams according to both their orbital angular momentum and radial topological numbers using a flow of two concatenated deep neural networks. The first network serves as a transfer function from experimentally-generated to ideal numerically-generated data, while using a unique "Histogram Weighted Loss" function that solves the problem of images with limited significant information. The second network acts as a spatial-modes classifier. Our method uses only the intensity profile of modes or their superposition, making the phase information redundant.

A simplified approach to low-frequency coherent anti-Stokes Raman spectroscopy using a sharp spectral edge filter

Liqing Ren, Maor Asher, Omer Yaffe, Yaron Silberberg, and Dan Oron

Doc ID: 364589 Received 08 Apr 2019; Accepted 20 Jun 2019; Posted 24 Jun 2019  View: PDF

Abstract: Coherent anti-Stokes Raman scattering (CARS) found wide applications in biomedical research. Compared with alternatives, single-beam CARS is especially attractive at low frequencies. Yet, currently existing schemes necessitate a relatively complicated setup to perform high resolution spectroscopy. Here, we show that the spectral sharp edge formed by an ultra-steep long-pass filter is sufficient for performing CARS spectroscopy, simplifying the system significantly. We compare the sensitivity of the presented methodology with available counterparts both theoretically and experimentally. Importantly, we show that this method is the simplest and most suitable for vibrational imaging and spectroscopy in the very low-frequency regime (<200cm-1).

Optical Analysis of the Refractive Index and Birefringence of Hexagonal Boron Nitride from the Visible to Near-Infrared

Kyoungsik Yu, Yoonhyuk Rah, Sejeong KIM, and Yeonghoon Jin

Doc ID: 366715 Received 07 May 2019; Accepted 20 Jun 2019; Posted 20 Jun 2019  View: PDF

Abstract: Two-dimensional materials such as hexagonal boron nitride (hBN), graphene, and transition metal dichalcogenides have drawn great attention in various fields of photonics and electronics. Among them, hBN has recently emerged as a promising material platform to study integrated quantum photonics due to its ultrabright quantum light emission capabilities. However, the fundamental optical properties of hBN have not yet been investigated in the visible and near-infrared (NIR) spectrum thoroughly. In this letter, we report the refractive indices of hBN thin films in the visible to NIR range. To the best of our knowledge, this is the first experimental observation of hBN birefringence. Accurate parameters of refractive indices enable more precise design of hBN-based photonic devices in the integrated photonics platforms.

Spatio-spectral features of soliton-assisted random laser in liquid crystals

Gaetano Assanto, sreekanth Perumbilavil, and Martti Kauranen

Doc ID: 368474 Received 24 May 2019; Accepted 20 Jun 2019; Posted 20 Jun 2019  View: PDF

Abstract: We report on novel features of random lasers assisted by near-infrared spatial solitons in nematic liquid crystals. Specifically, we study the role of light-induced reorientational waveguides (nematicons) on the spatial and spectral distributions of the laser modes. We show that the spatially spiky character of the laser emission propagating backwards with respect to the pump tends to disappear in the forward direction, due to the soliton confinement of the generated light. Moreover, the spectral features associated to various random laser resonances appear to merge upon guided-wave propagation along the nematicon, making the nematicon-aided random laser a bidirectional device with distinct emission properties at the two opposite outputs.

Kerr-lens mode-locked Pr3+:LuLiF4 laser

Yuxia Zhang, Rulin Miao, Dazhi Lu, Mauro Tonelli, jiyang wang, Haohai Yu, and Huaijin Zhang

Doc ID: 368753 Received 28 May 2019; Accepted 20 Jun 2019; Posted 20 Jun 2019  View: PDF

Abstract: We demonstrated the Kerr-lens mode-locked Pr:LuLiF4 laser pumped by a blue laser diode (LD). By theoretical calculation of the group velocity dispersion in the laser gain, the compensation was employed for the realization the continuous-wave mode-locked laser at the wavelength of 604 nm with the pulse width of 1.1 ps which should be the shortest pulse width in the Pr3+ ion doped crystal lasers pumped with LDs to the best of our knowledge. It can be believed that the present Pr:LuLiF4 laser should provide some inspirations for the development of the blue LD pumped visible lasers especially in the mode-locking laser operation.

Lithography-Free, Manganese-Based Ultra-Broadband Absorption through Annealing-Based Deformation of Thin Layers into Metal-Air Composites

Majid Aalizadeh, Amin Khavasi, Bayram Butun, and Ekmel Ozbay

Doc ID: 369951 Received 12 Jun 2019; Accepted 19 Jun 2019; Posted 20 Jun 2019  View: PDF

Abstract: Fabrication, characterization, and analysis of an ultra-broadband lithography-free absorber is presented. An over 94% average absorption is experimentally achieved in the wavelength range of 450-1400 nm. This ultra-broadband absorption is obtained by a simple annealed tri-layer metal-insulator-metal (MIM) configuration. The metal used in the structure is Manganese (Mn), which also makes the structure cost-effective. It is shown that the structure retains its high absorption for TM polarization, up to 70 degrees, and, for TE polarization, up to 50 degrees. Moreover, the physical mechanism behind this broadband absorption is explained. Being both lithography-free and cost-effective, the structure is a perfect candidate for large-area and mass production purposes.

Dual-wavelength-band subwavelength grating coupler operating in the near infrared and extended shortwave infrared

Wen Zhou and Hon Tsang

Doc ID: 367418 Received 13 May 2019; Accepted 19 Jun 2019; Posted 20 Jun 2019  View: PDF

Abstract: We show that dual-wavelength-band (DWB) subwavelength grating couplers (SWGCs) can be designed for simultaneous coupling of the near-infrared (near-IR) and extended shortwave-infrared (SWIR) fundamental transverse electric (TE) polarized light at a same diffraction angle. Numerical simulation predicts the coupling efficiencies (CEs) of larger than 34% for the DWB SWGCs operating in the S/C band (1.48/1.55 μm) and extended SWIR band (1.8–2.8 μm) with a widely and continuously tailorable peak wavelength separation between 250 and 1250 nm. The fabricated DWB SWGCs with peak wavelengths of (1.56, 2.255) μm and (1.487, 2.331) μm respectively obtain CEs of (20.2, 25.8)% and (20.6, 26.9)%, 3-dB bandwidths of (38.0, 42.6) nm and (39.0, >59.4) nm at a diffraction angle of 2°.

Adaptive high resolution Linnik interferometry for 3D measurement of microparticles

Benedikt Allendorf, Eireen Käkel, Uh-Myong Ha, Sebastian Hagemeier, Peter Lehmann, and Hartmut Hillmer

Doc ID: 366690 Received 06 May 2019; Accepted 19 Jun 2019; Posted 19 Jun 2019  View: PDF

Abstract: Tailored 3D microparticles and nanostructures lead to increasing possibilities in manufacturing and functionalization for instance in semiconductor industry or biomedical application. In this interdisciplinary study we investigate the parallel production of such particles by using nanoimprint lithography in combination with their characterization based on interference microscopy. The metrological inspection tends to an universal measurement solution where the sample is optically compared to a master object.

Nanosecond photonic switch architectures demonstrated in an all-digital monolithic platform

Nicolas Dupuis, Jonathan Proesel, Herschel Ainspan, Christian Baks, Mounir Meghelli, and Benjamin Lee

Doc ID: 367549 Received 15 May 2019; Accepted 19 Jun 2019; Posted 19 Jun 2019  View: PDF

Abstract: We present an all-digital, fully programmable, nanosecond-scale photonic switch platform, mono- lithically integrating electronics for actuation, tuning, and power-monitoring alongside switching elements, resulting in a scalable, packageable solution for high- radix photonic switch fabrics. Utilizing this platform, we achieve record loss and extinction performances comprising a 2x2 Mach Zehnder switch with 0.8 dB of loss and 28 dB extinction and a 2x2 nested Mach Zehnder switch with 1.3 dB of loss and 38 dB extinction.

Loss tailoring of high power broad area diode lasers

Lijie Wang, Cunzhu Tong, Shili Shu, Sicong Tian, Fangyuan Sun, Yufei zhao, Huanyu Lu, Xin Zhang, Guanyu Hou, and Lijun Wang

Doc ID: 367578 Received 15 May 2019; Accepted 19 Jun 2019; Posted 19 Jun 2019  View: PDF

Abstract: Broad area diode lasers (BALs) with high power are highly desirable for a variety of applications. However, such lasers suffer from strongly deteriorated beam quality due to multimode behavior in the lateral direction. In this paper, we present an approach to flexibly tailor the optical loss of different-order lateral modes by etching micro-holes on the laser mesa with controlled position and numbers. Through arranging the micro-holes at the peak position of high-order lateral modes with increasing number from the mesa center to both edges, high-order modes are suppressed due to a larger propagation loss than the fundamental mode. As a result of enhanced mode discrimination, we demonstrate that this technique provides a much improved beam quality and about two times higher brightness for 100 μm wide BAL, while maintaining high power and slope efficiency output.

Distributed Bragg reflector fiber laser directly written in a composite fiber manufactured by melting phosphate glass in a silica tube

Andrey Rybaltovsky, Olga Egorova, Sergei Zhuravlev, Boris Galagan, Sergei Sverchkov, Boris Denker, and Sergey Semjonov

Doc ID: 367417 Received 15 May 2019; Accepted 18 Jun 2019; Posted 19 Jun 2019  View: PDF

Abstract: We demonstrate a single-frequency distributed Bragg reflector (DBR) fiber laser based on the novel erbium-doped composite fiber fabricated by melting phosphate glass in a silica tube. The fabricated composite fiber was single-mode at the wavelength of 1.55 µm; the measured cutoff wavelength was 1.4 μm. The composite fiber was photosensitive to irradiation at the wavelength of 193 nm. Using the phase mask method, the DBR fiber laser cavity with the total length of 21 mm was inscribed directly into the erbium-doped composite fiber. A stable single-frequency regime of the fabricated DBR laser at the wavelength of 1565 nm is demonstrated.

Ultraviolet photoacoustic remote sensing microscopy

Nathaniel Haven, Kevan Bell, Pradyumna Kedarisetti, John Lewis, and Roger Zemp

Doc ID: 367179 Received 13 May 2019; Accepted 18 Jun 2019; Posted 20 Jun 2019  View: PDF

Abstract: Traditional histopathology involves fixing, sectioning and staining protocols that are time consuming and subject to staining variability. Here we present ultraviolet photoacoustic remote sensing (UV-PARS) microscopy, which is capable of imaging cell nuclei without the need for exogenous stains or labelling. Our reflection-mode approach is non-contact and has the potential to provide useful histological information without laborious sample preparation steps. Tumor cell cultures and excised tissue samples were imaged with 0.7-μm resolution and signal-to-noise ratios as high as 53 dB with close agreement to traditional H&E staining.

Generation of Gaussian-modulated entangled states for continuous variable quantum communication

Ning Wang, shanna du, wenyuan liu, Xuyang Wang, and Yongmin Li

Doc ID: 368457 Received 27 May 2019; Accepted 17 Jun 2019; Posted 19 Jun 2019  View: PDF

Abstract: We present and demonstrate a high-efficiency and compact scheme for generating Gaussian-modulated Einstein-Podolsky-Rosen (EPR) entangled optical fields by injecting a modulated signal field into a non-degenerate optical parametric amplifier (NOPA). We perform quantum analysis of the scheme and derive the variance of the output signal (idler) mode and the quantum entanglement between the output signal and idler modes from the NOPA. An experimental study is also presented with different Gaussian modulation depths, showing that the modulation of the injected signal field successfully enlarges the distribution of the field quadratures of the EPR source in phase space and has negligible effect on the entanglement quality. The experimental observations have good agreement with theoretical analysis. Our scheme can be used readily in the continuous variable quantum key distribution protocol with modulated entangled states.

Si quantum dots enhanced hydrogen bonds networks of liquid water in Stimulated Raman scattering process

Ying Wang, fabing Li, zhanlong li, chenglin sun, and zhiwei men

Doc ID: 368271 Received 24 May 2019; Accepted 17 Jun 2019; Posted 20 Jun 2019  View: PDF

Abstract: Stimulated Raman scattering (SRS) of different sizes (2 and 5 nm) silicon quantum dots (Si QDs) water solutions are investigated using Nd:YAG laser. Since the strong and weak hydrogen bonds are formed by the charges transfer between water molecules and Si QDs, two SRS peaks of OH stretching vibrations of Si QDs solutions are observed in the forward direction. Simultaneously, characteristic feature peaks related to the interaction between OH groups and excess electrons are obtained in the backward SRS of 2 nm Si QDs solutions. The excess electrons induce a strong electrostatic field, leading water to formation of ice-VIII structure.

Non-Markovian spontaneous emission interference near a MoS₂ nanodisk

Ioannis Thanopulos, Vasilios Karanikolas, and Emmanuel Paspalakis

Doc ID: 365840 Received 23 Apr 2019; Accepted 17 Jun 2019; Posted 18 Jun 2019  View: PDF

Abstract: We propose a nanophotonic structure that gives high-degree quantum interference in the spontaneous emission of a quantum emitter in conjunction with strong light-matter coupling and non-Markovian dynamics. Specifically, we study the spontaneous emission dynamics of a three-level V-type quantum emitter close to a MoS₂ nanodisk. We combine quantum dynamics calculations with electromagnetic calculations and find reversible population dynamics in the quantum emitter together with high-degree quantum interference created by the nanodisk. A rich population dynamics is obtained depending on the energy of the quantum emitter with respect to the energies of the exciton-polariton resonances of the MoS₂ nanodisk, the distance of the quantum emitter from the nanodisk, and the initial state of the quantum emitter. Our results have potential applications in emergent quantum technologies.

An FCC-compliant millimeter wave ultra-wideband pulse generator based on optoelectronic oscillation

Wei Li, Sha Zhu, xiaojie fan, Ninghua Zhu, and Ming Li

Doc ID: 366876 Received 07 May 2019; Accepted 17 Jun 2019; Posted 17 Jun 2019  View: PDF

Abstract: We report a photonic scheme to generate millimeter wave ultra-wideband (MMW-UWB) pulse based on optoelectronic oscillation (OEO). Normally, a millimeter wave signal is essential for the generation of MMW-UWB pulse. The key novelty of our work is that no millimeter wave signal is required. The MMW-UWB pulses are directly generated by truncating an OEO signal into pulses. The principle behind the proposed scheme is analyzed in detail. A proof-of-concept experiment shows that the generated MMW-UWB pulses fit the Federal Communications Commission (FCC) spectral mask very well.

Quantitative phase imaging with molecular vibrational sensitivity

Takuro Ideguchi, Miu Tamamitsu, Keiichiro Toda, and Ryoichi Horisaki

Doc ID: 362759 Received 19 Mar 2019; Accepted 17 Jun 2019; Posted 18 Jun 2019  View: PDF

Abstract: Quantitative phase imaging (QPI) quantifies the sample-specific optical-phase-delay enabling objective studies of optically-transparent specimens such as biological samples, but lacks chemical sensitivity limiting its application to morphology-based diagnosis. We present wide-field molecular-vibrational microscopy realized in the framework of QPI utilizing mid-infrared photothermal effect. Our technique provides mid-infrared spectroscopic performance comparable to that of a conventional infrared spectrometer in the molecular fingerprint region of 1,450 – 1,600 cm-¹ and realizes wide-field molecular imaging of silica-polystyrene beads mixture over 100 μm × 100 μm area at 1 frame per second with the spatial resolution of 430 nm and 2 - 3 orders of magnitude lower fluence of ~10 pJ/µm² compared to other high-speed label-free molecular imaging methods, reducing photodamages to the sample. With a high-energy mid-infrared pulse source, our technique could enable high-speed, label-free, simultaneous and in-situ acquisition of quantitative morphology and molecular-vibrational contrast, providing new insights for studies of optically-transparent complex dynamics.

Intensity and spin anisotropy of three-dimensional polarization states

Jose Gil, Andreas Norrman, Ari Tapio Friberg, and Tero Setala

Doc ID: 366551 Received 20 May 2019; Accepted 16 Jun 2019; Posted 19 Jun 2019  View: PDF

Abstract: Anisotropy is a natural feature of polarization states and only fully random three-dimensional (3D) states exhibit complete isotropy. In general, differences between the strengths of the electric field components along the three orthogonal directions give rise to intensity anisotropy. Moreover, polarization states involve an average spin whose inherent vectorial nature constitutes a source of spin anisotropy. In this work, appropriate descriptors are identified to characterize quantitatively the levels of intensity anisotropy and spin anisotropy of a general 3D polarization state, leading to a novel interpretation for the degree of polarimetric purity as a measure describing the overall polarimetric anisotropy of a 3D optical field. The mathematical representation as well as the physical features of completely intensity-isotropic 3D polarization states with maximal spin anisotropy are also examined. The results provide new insights into the polarimetric field structure of random 3D electromagnetic light states.

Protruding-shaped SiO2-Microtip: From Fabrication Innovation to Micro-Photonic Device Construction

Lingxin Kong, Yanxi Zhang, Weigang Zhang, Zhe Li, Lin Yu, Tieyi Yan, Pengcheng Geng, and wang biao

Doc ID: 366570 Received 02 May 2019; Accepted 16 Jun 2019; Posted 19 Jun 2019  View: PDF

Abstract: In this letter, we first proposed a new technology to prepare protruding-shaped SiO2-microtips (PSSMs): Transient Spinning Technology (TST). By designing the operation steps and controlling the discharge parameters of fiber splicing machine (Furukawa S178a), the protruding-shaped SiO2-microtips with different structural parameters can be fabricated simply, quickly and efficiently. Two kinds of microtip photonic devices were designed: 1. a high-sensitivity gas refractive index (RI) Mach-Zehnder interferometer (MZI) sensor based on the coned-microtip; 2. an efficient LP11 mode selective exciter based on the lensd-microtip. Furthermore, the PSSMs have more potential applications, such as optical fiber tweezers, optical fiber Raman probes and scanning near-field optical microscopy.

Photonic integrated circuit extended cavity passivelymode-locked dual absorber symmetric ring laser

Mu-Chieh Lo, dominik auth, Christoph Weber, Patrick Fiala, Pascal Sauer, Guillermo Carpintero, and Stefan Breuer

Doc ID: 368109 Received 27 May 2019; Accepted 14 Jun 2019; Posted 19 Jun 2019  View: PDF

Abstract: A photonic integrated circuit extended cavity passively mode-locked semiconductor ring laser with two sat- urable absorbers in a symmetric ring geometry fab- ricated using an InP generic integration technology platform is presented for the first time. The laser emits 1.4 ps short optical pulses with a time-bandwidth- product of 0.96 (Gaussian shaped pulses) at a funda- mental repetition rate of .3 GHz. The laser exhibits a beat-note line width of 80kHz, corresponding to a pulse-to-pulse timing jitter of 31.7 fs. The emission is centered at 1570 nm and maximum spectral bandwidth amounts to 10.2 nm (-3 dB) and 19.7 nm (-20 dB).

Four-port SNAP microresonator device

Manuel Crespo Ballesteros, Yong Yang, and Misha Sumetsky

Doc ID: 367889 Received 17 May 2019; Accepted 14 Jun 2019; Posted 17 Jun 2019  View: PDF

Abstract: It is well known from quantum mechanics that the transmission amplitude of a symmetric double-barrier structure can approach unity at the resonance condition. Similar phenomenon is observed in optics for light which propagates between two waveguides weakly coupled through a microresonator. Examples of microresonators used for this purpose include ring, photonic crystal, toroidal, and bottle microresonators. However, ring and photonic crystal photonic circuits, once fabricated, cannot be finely tuned to arrive at the mentioned resonant condition. In turn, it is challenging to predictably adjust coupling to toroidal and bottle microresonators by translating the input-output microfibers since the modes of these resonators is difficult to separate spatially. Here we experimentally demonstrate a four-port micro-device based on a SNAP microresonator introduced at the surface of an optical fiber. The eigenmodes and corresponding eigenwavelengths of this resonator are clearly identified for both polarization states by the spectrograms measured along the length of the fiber. This allows us to choose the resonant wavelength and simultaneously determine the positions of the input-output microfiber tapers to arrive at the required resonance condition.

Single-pass, second harmonic geneation of high power, ultrafast mid-IR Cr2+:ZnS laser at 60 nm

Anirban Ghosh, Deepika Yadav, and Goutam K. Samanta

Doc ID: 367880 Received 17 May 2019; Accepted 14 Jun 2019; Posted 14 Jun 2019  View: PDF

Abstract: We report on a compact and simple ultrafast source producing tunable radiation in the near-IR wavelength range. Based on single-pass frequency-doubling of an ultrafast Cr2+:ZnS laser at 60 nm with pulse width of 43 fs at a repetition rate of 80 MHz in MgO:PPLN crystal, the source produces maximum average output power of ~2.43 W tunable across 1137-1200 nm with a maximum single-pass conversion efficiency as high as 65%. Without use of any pulse compression technique, the source produces output pulses in Gaussian shape with measured pulse width of ~60 fs and spectral width of 39 nm centered at 1180 nm corresponding to the time-bandwidth product of 0.5. The output beam has Gaussian spatial profile with measured M²<1.32 and a peak-to-peak power fluctuation of 3% over 2 hours. Using two different MgO:PPLN crystals of length 1 mm and 2 mm, we observe that the highest conversion efficiency appears at lower pump powers. Furthermore, we have studied the focusing dependent SHG efficiency and observed that at high parametric gain regime the optimum SHG efficiency of an ultrafast pulse laser, even in presence of temporal walk-off, is achieved at low pump focusing condition.

Photonic vector mm-wave signal generation by optical dual-SSB modulation and a single push-pull MZM

xiaolong Pan, Xiangyu Liu, Hongxin Zhang, Chuxuan Wang, xishuo wang, Yueming Zhang, and Dongsheng Ran

Doc ID: 368485 Received 27 May 2019; Accepted 14 Jun 2019; Posted 19 Jun 2019  View: PDF

Abstract: We propose and experimentally demonstrate single-sideband (SSB) photonic vector millimeter-wave (mm-wave) signal generation enabled by optical dual-SSB modulation and a single push-pull Mach-Zehnder modulator (MZM). We use software-based digital signal processing (DSP) to generate the dual-SSB driving signal for the push-pull MZM. The dual-SSB driving signal has a vector-modulated sideband and an unmodulated sideband, which are spaced by our desired mm-wave carrier frequency. After linear modulation of the push-pull MZM, optical filtering, and single-ended photodiode (PD) detection, we can get an electrical mm-wave signal displaying the same vector modulation as the aforementioned vector-modulated sideband. Based on our proposed scheme, we experimentally demonstrate the generation and transmission of 40-GHz mm-wave signal carrying 1-Gbaud 16-ary quadrature-amplitude-modulation (16QAM) or 4-Gbaud quadrature-phase-shift-keying (QPSK) transmitter data over 10-km single-mode fiber-28 (SMF-28) and 0.5-m air-space link, with a bit-error-ratio (BER) less than the hard-decision forward-error-correction (FEC) threshold. © 2019 Optical Society of America

Fabry–Pérot cavity based contact force sensor with high precision and broad operational range

Jitendra Dash, Zhengyong Liu, Dinusha Gunawardena, and Hwa Yaw Tam

Doc ID: 365343 Received 17 Apr 2019; Accepted 13 Jun 2019; Posted 18 Jun 2019  View: PDF

Abstract: A novel, compact and robust contact force sensor based on a micro length single mode fiber (SMF) incorporated in a cleaved micro air cavity (MAC) is proposed. The fabrication process involves splicing of SMF with a hollow core fiber (HCF) followed by cleaving of the MAC and insertion of SMF into the MAC. The force sensing mechanism is based on the movement of the micro SMF inside the cleaved MAC. The total length of the probe varies between 300-500 µm making it bent proof. Due to the all silica based structure, the sensing capability of the probe is demonstrated for low (0 to 1000 mN) as well as high range of force (1 to 10 N) measurements. The optimized structure shows a maximum force sensitivity of 14.2 pm/mN with a negligible temperature dependence of 0.4 pm/°C. The performance of the sensor is verified using an FEM based software. The proposed probe has a linear response, negligible hysteresis and repeatability error making it suitable for biomedical sensing and robotic applications.

Quasinormal-mode analysis of grating spectra at fixed incidence angles

Alexandre Gras, Wei Yan, and Philippe Lalanne

Doc ID: 367881 Received 17 May 2019; Accepted 13 Jun 2019; Posted 14 Jun 2019  View: PDF

Abstract: Grating spectra exhibit sharp variations of the scattered light, known as grating anomalies. The latter are due to resonances that have fascinated specialists of optics and physics for decades and are nowadays used in many applications. We present a comprehensive theory of grating anomalies, and develop a formalism to expand the field scattered by metallic or dielectric gratings into the basis of its natural resonances, thereby enabling the possibility to reconstruct grating spectra measured for fixed illumination angles as a sum over every individual resonance contribution with closed-form expressions. This gives physical insights into the spectral properties and a direct access to the resonances to engineer the spectral response of gratings and their sensitivity to tiny perturbations.

Self-assembled axicon lens in integrated optical fiber

Christopher Holmes and Peter Smith

Doc ID: 363551 Received 28 Mar 2019; Accepted 13 Jun 2019; Posted 17 Jun 2019  View: PDF

Abstract: This work reports the fabrication of an integrated axicon lens within a monolithic fibre-upon-planar format. The lens is self-assembled around a tapered optical fibre during flame hydrolysis planarization. The formed lens approximates an oblate axicon that upon launch generates a quasi-Bessel beam, guided in the planar optical layer of the substrate. Experimental observations are theoretically concurred using Fourier-based beam propagation.

Nonlinear reconstruction of weak optical diffused images under turbid water

Zhaolu Wang, Hongjun Liu, Nan Huang, Yongbin Zhang, and Jiao Chi

Doc ID: 360405 Received 18 Feb 2019; Accepted 13 Jun 2019; Posted 18 Jun 2019  View: PDF

Abstract: The forward scattering noise may degrade the imaging resolution and diffuse the image in turbid water. The reconstruction of diffused images hidden by forward scattering noise is crucial for underwater imaging. To overcome the limitation of forward scattering for optical imaging in turbid water, a nonlinear image reconstruction technology is proposed in experiment. We experimentally demonstrated the reconstruction of the diffused images under turbid water via signal seeded incoherent modulation instability in a nonlinear photorefractive crystal. The reconstructed image with high quality and the minimum resolution of 28.51 lp/mm are observed in the experiment. This is the first time, to the best of our knowledge, using spatial modulation instability effect to process underwater weak optical diffused images in the experiment.

Highly efficient narrow-band absorption of a graphene-based Fabry–Pérot structure at telecommunication wavelengths

Kun Zhou, Qiang Cheng, Jinlin Song, Lu Lu, and Zixue Luo

Doc ID: 366435 Received 01 May 2019; Accepted 13 Jun 2019; Posted 14 Jun 2019  View: PDF

Abstract: We numerically investigate a novel graphene-based Fabry–Pérot (GFP) structure to enhance the light-matter interaction of graphene at telecommunication wavelengths, and highly efficient narrow-band absorption is achieved. The absorptance of the GFP structure can reach near-unity by optimizing the position of graphene in the dielectric layer, and the localized absorptance of graphene at telecommunication wavelengths can be improved from 2.3% to 83.2%, which is attributed to the strong field confinement of Fabry–Pérot (FP) resonance in the dielectric layer. The remarkable enhancement of graphene absorption can be acquired for both TM and TE polarizations. Such a graphene-based structure enables tunable operating wavelength by adjusting geometrical parameters to realize the spectral selectivity of the system in the near-infrared range. Furthermore, the optimized GFP (OGFP) structure possesses excellent spectral selectivity with the full width at half-maximum (FWHM) of 33 nm. The meaningful improvement and tunability of graphene absorption can provide a promising prospect for the realization of high-performance graphene-based optoelectronic devices.

Tunable coupled-cavity semiconductor laser based on half-wave bow-tie coupler

Jian-Jun He, jia Guo, Yimin Xia, and Xiaolu Liao

Doc ID: 367283 Received 09 May 2019; Accepted 12 Jun 2019; Posted 17 Jun 2019  View: PDF

Abstract: We propose and experimentally demonstrate a widely tunable coupled cavity semiconductor laser based on a novel half-wave bow-tie coupler. The laser comprises two resonate cavities connected through the bow-tie coupler consisting of two back-to-back corner reflectors connected with a short waveguide, which produces half-wave cross-coupling phase with an optimum coupling coefficient for achieving high mode selectivity. No complex grating or multiple epitaxial growth is needed. By tuning a single electrode at a fixed temperature, 29.6nm wavelength tuning covering 38 channels with 100GHz frequency spacing is achieved experimentally, with side mode suppression ratio (SMSR) of about 40dB.

Optical Generation and Control of Spatial Riemann Waves

domenico bongiovanni, Benjamin Wetzel, Pengzhen Yang, Yi Hu, Yujie Qiu, Jingjun Xu, Stefan Wabnitz, Zhigang Chen, and Roberto Morandotti

Doc ID: 363703 Received 29 Mar 2019; Accepted 12 Jun 2019; Posted 17 Jun 2019  View: PDF

Abstract: We extend the concept of Riemann waves to the spatial domain, and demonstrate for the first time Riemann beams with a propagation scenario allowing controllable shock formation in a nonlinear optical system. Similar to their standard counterparts, “shifted” Riemann waves are characterized by a local propagation speed proportional to their local amplitude. Their steepening dynamics can be judiciously controlled by the introduction of an additional phase term. In particular, Riemann waves are generated by properly tailoring the initial phase of an optical beam propagating through a thermal solution of m-cresol/nylon mixture that exhibits a giant self-defocusing nonlinearity. Experimental results show a controllable steepening and shock wave behavior, in good agreement with the prediction from the simple inviscid Burgers’ equation

Microcavity-based narrowband parametric amplifier for carrier recovery in optical coherent self-homodyne detection

Yong Geng, Wenwen Cui, qing wen, Boyang Wang, Qiang Zhou, Bao-Jian Wu, and Heng Zhou

Doc ID: 363657 Received 29 Mar 2019; Accepted 12 Jun 2019; Posted 14 Jun 2019  View: PDF

Abstract: We demonstrate all-optical carrier recovery exploring optical parametric amplification (OPA) in monolithic high finesse silicon nitride micro-ring cavity. Comparing with non-resonant OPA process in nonlinear waveguides, cavity-based OPA allows much narrower gain bandwidth by manipulating the intracavity light interactions with controllable parametric gain, so that to facilitate high resolution carrier extraction without needing a large guard band between the carrier tone and data spectrum. Here, we achieve narrowband OPA with 22.0 dB peak gain and bandwidth as low as 15.2 MHz in a 100-μm radius micro-ring cavity, which is applied to implement carrier recovery of 16QAM optical orthogonal-frequency-division-multiplexing data signal. Highly coherent phase is conserved between the recovered carrier tone and the original data, enabling self-homodyne detection with high data quality and minimized electrical compensation. Our study holds potential to constitute energy-friendly coherent receivers.

Few-cycle 1.9-μm pulse generation in multiple-crystal optical parametric amplifier

Zuofei Hong, Feilong Hu, Xianglong Fu, Wei Cao, Qingbin Zhang, and Peixiang Lu

Doc ID: 367303 Received 10 May 2019; Accepted 12 Jun 2019; Posted 12 Jun 2019  View: PDF

Abstract: A multiple-crystal OPA design is reported for efficiently generating few-cycle 1.9-μm laser pulses. Different spectral regions of the idler pulse are successively amplified in three nonlinear crystals with delicately adjusted phase-matching angles, a broadband spectrum supporting a 3-cycle TL pulse duration is obtained. Near-TL duration of 21.5 fs is realized by simple compression in a silicon window. Owing to sufficient exploit of the pump energy in the crystals, the total conversion efficiency of 31.3% is achieved with the idler pulse energy of 65.8 µJ. The gain bandwidth in multiple-crystal OPA is markedly broadened compared to OPA using a single thick crystal, meanwhile the high efficiency is preserved. Further energy scaling of the proposed scheme is potentially feasible using the dual-chirped OPA geometry.

Threshold behaviour of optical frequency comb self-generation in an InAs/InGaAs quantum dot laser

Christoph Weber, Lorenzo Columbo, Mariangela Gioannini, Stefan Breuer, and Paolo Bardella

Doc ID: 367389 Received 13 May 2019; Accepted 12 Jun 2019; Posted 13 Jun 2019  View: PDF

Abstract: We report on a significant reduction of both the radio-frequency beat note line width at 40.7 GHz and the integrated relative intensity noise of a 1 mm long edge-emitting monolithic Fabry-Perot InAs/InGaAs quantum dot semiconductor laser emitting from the ground state at 1250nm by injection current control. For increasing injection currents, first an unlocked multi-mode behaviour is observed and then, at a certain current above lasing threshold, self-locking of the longitudinal modes due to internal non-linear effects occurs yielding a beat line width of 20 kHz (−3 dB) in contrast to tens of megahertz for lower injection currents. These results are confirmed by simulations.

Narrow-Linewidth Mid-Infrared Quantum Cascade Laser by Stabilization to an Optical Delay Line

Atif Shehzad, Pierre Brochard, Renaud Matthey, Thomas Südmeyer, and Stephane Schilt

Doc ID: 366730 Received 21 May 2019; Accepted 11 Jun 2019; Posted 13 Jun 2019  View: PDF

Abstract: We present a mid-infrared quantum cascade laser (QCL) with a sub-10-kHz full width at half maximum linewidth (at 1-s integration time) achieved by stabilization to a free-space optical delay line. The linear range in the center of a fringe detected at the output of an imbalanced Mach-Zehnder interferometer implemented with a short free-space pathlength difference of only 1 m is used as frequency discriminator to detect the frequency fluctuations of the QCL. Feedback is applied to the QCL current to lock the laser frequency to the delay line. Using this method for the first time in the mid-infrared in a simple self-homodyne configuration, we have been able to reduce the frequency noise power spectral density of the QCL by almost 40 dB below 10-kHz Fourier frequency, leading to a linewidth reduction by a factor of almost 60 compared to the free-running laser. The present limits of the setup are assessed and discussed.

Machine learning based pulse characterisation inmode-locked lasers

Alexey Kokhanovskiy, Anastasia Bednyakova, Evgeny Kuprikov, Aleksey Ivanenko, Mikhail Dyatlov, Daniel Lotkov, Sergey Kobtsev, and Sergei Turitsyn

Doc ID: 367781 Received 16 May 2019; Accepted 11 Jun 2019; Posted 12 Jun 2019  View: PDF

Abstract: By combining machine learning methods and the dispersive Fourier transform we demonstrate, to the best of our knowledge, for the first time a possibility to determine the temporal duration of picosecond-scale laserpulses using nanosecond photodetector. A fiber figure of eight (F-8) laser with two amplifiers in a resonator was used to generate pulses with duration varying from 25 to 160 ps and spectral width varied in the range of 0.75 to 12 nm. Average power of the pulses was in rangefrom 40 to 300mW. The trained artificial neural networkmakes it possible to predict the pulse duration with themean agreement of 95%. The proposed technique pavesthe way to creating compact and low cost feedback forcomplex laser systems.

High-efficiency four-wave mixing beyond pure electromagnetically induced transparency treatment

Haichao Li, Guo Ge, and M. Suhail Zubairy

Doc ID: 368112 Received 21 May 2019; Accepted 11 Jun 2019; Posted 13 Jun 2019  View: PDF

Abstract: We present a theoretical study of high-efficiency four-wave mixing (FWM) sum-frequency generation beyond pure electromagnetically induced transparency (EIT) technique in a five-level atomic system. In our FWM scheme, with the assistance of two Λ-type subsystems utilized to create EIT and Autler-Townes splitting (ATS), a synergetic mechanism of EIT and ATS or a dual-ATS mechanism is induced. These novel mechanisms can have a significant impact on the FWM process in the optically thick medium and the FWM efficiency can be several orders of magnitude larger than that obtained from the pure EIT method. Our study opens up a new perspective for exploring enhanced quantum nonlinear optical phenomena.

Watt-level All-fiber Optical Parametric Chirped-Pulse Amplifier Working at 1300 nm

Yukun Qin, Yi-Hsin Ou, Benjamin Cromey, Orkhongua Batjargal, Jennifer Barton, and Khanh Kieu

Doc ID: 364754 Received 11 Apr 2019; Accepted 11 Jun 2019; Posted 12 Jun 2019  View: PDF

Abstract: We report Watt-level average output power near 1300 nm from an all-fiber ultrafast optical parametric chirped-pulse amplifier. A compressed output pulse duration of ~300 fs was achieved. Multiphoton imaging of a variety of samples carried out with this light source shows a good signal to noise ratio. With the demonstrated imaging capability, we believe that this high-power ultrafast laser source addresses a key need in deep tissue multiphoton microscopy.

High-speed and high-precision torsion sensor based on polarization-induced microwave photonic phase shifting

Jianping Yao, Bin Wang, Xinyu Fan, and Weifeng Zhang

Doc ID: 366188 Received 26 Apr 2019; Accepted 10 Jun 2019; Posted 11 Jun 2019  View: PDF

Abstract: We propose and experimentally demonstrate a technique to achieve high-speed and high-precision torsion sensing based on polarization-induced microwave photonic phase shifting. In the proposed system, a section of single-mode fiber (SMF) is used as a sensor that is incorporated into a microwave photonic phase shifter (MPPS). The MPPS consists of a laser source, a polarization modulator (PolM), an optical bandpass filter (BPF), a SMF, a polarizer, and a photodetector (PD). The phase shift of the microwave signal is a linear function of the twist angle of the SMF. An IQ detection module is utilized to measure the microwave phase shift. The performance of the proposed torsion sensor is experimentally evaluated. A measurement range of over 180° and a sensing accuracy of 0.03° are realized at an ultrahigh speed of 1 M samples/s, with low strain and temperature cross-sensitivity.

III-V on Silicon Avalanche Photodiodes by Heteroepitaxy

Yuan Yuan, Daehwan Jung, Keye Sun, Jiyuan Zheng, Andrew Jones, John Bowers, and Joe Campbell

Doc ID: 364252 Received 05 Apr 2019; Accepted 10 Jun 2019; Posted 17 Jun 2019  View: PDF

Abstract: We demonstrate a III-V avalanche photodiode (APD) grown by heteroepitaxy on silicon. This InGaAs/InAlAs APD exhibits low dark current, gain > 20, external quantum efficiency > 40%, and similar low excess noise, k ~0.2, as InAlAs APDs on InP.

CEP-stable high-energy ytterbium doped fiber amplifier

Michele natile, Anna Golinelli, Loïc Lavenu, Florent Guichard, Marc Hanna, Yoann Zaouter, ronic chiche, Xiaowei Chen, Jean-Francois Hergott, Willem Boutu, Hamed Merdji, and Patrick Georges

Doc ID: 364621 Received 10 Apr 2019; Accepted 10 Jun 2019; Posted 18 Jun 2019  View: PDF

Abstract: We report on the CEP stabilization of an Yb-doped fiber amplifier system delivering 30 µJ pulses at 100 kHz repetition rate. A single shot, every shot, measurement of the CEP stability based on a simple f-2f interferometer is performed, yielding a CEP standard deviation of 320 mrad rms over 1 s. Long-term stability is also assessed, with 380 mrad measured over one hour. This level of performance is allowed by a hybrid architecture including a passively CEP-stabilized front-end based on difference frequency generation, and an active CEP stabilization loop for the fiber amplifier system, acting on a telecom-grade integrated LiNbO3 phase modulator. Together with recent demonstrations of temporal compression down to the few-cycle regime, the presented results demonstrate the relevance of Yb-doped high repetition rate laser for attoscience.

Investigation on binding energy and reduced effective mass of exciton in organic-inorganic hybrid lead perovskite films by a pure optical method

Yang Liu, ju wang, ning zhu, Wei Liu, Cuncun Wu, Congyue Liu, Lixin Xiao, Zhijian Chen Chen, and Shufeng Wang

Doc ID: 367606 Received 24 May 2019; Accepted 09 Jun 2019; Posted 13 Jun 2019  View: PDF

Abstract: The exciton binding energy and its reduced effective mass in hybrid lead perovskite, which play a key role in the process of excitons forming, largely determine the excellent optical properties of the perovskite materials, and hence the device performance. We introduce the systematic measurements on these two parameters of the organic-inorganic hybrid perovskite films of (MA/FA)Pb(Br/I)₃ by a unique temperature and density-resolved optical spectroscopic method. The method is simple and straight forward since it directly observed the exciton ionization and recombination. Our results described the fundamental photoelectric properties for understanding the excellent performance of the perovskite materials.

Integrated high-power germanium photodetectors assisted by light field manipulation

Yan Zuo, Yu Yu, Yu Zhang, De Zhou, and Xinliang Zhang

Doc ID: 366007 Received 29 Apr 2019; Accepted 09 Jun 2019; Posted 10 Jun 2019  View: PDF

Abstract: We experimentally demonstrate integrated high-power germanium photodetectors (Ge PDs) by means of light field manipulation. Compared to the conventional Ge PD, the proposed structures have more uniform light distributions in the absorption region. A maximum photocurrent of 27.1 mA at -3 V bias voltage is experimentally obtained, demonstrating a 50% more photocurrent generation under high power illumination. Bandwidth and modulated signal measurements also verify the improved power handling capability. The proposed high-power Ge PD with compact size and large fabrication tolerance will bring new applications for silicon photonics.

Photoacoustic thermorelaxation microscopy for thermal diffusivity measurement

Huazhen Chen, Yujiao Shi, and Da Xing

Doc ID: 367094 Received 08 May 2019; Accepted 09 Jun 2019; Posted 10 Jun 2019  View: PDF

Abstract: Thermal diffusivity is one of the main parameters to characterize the thermo-physical properties of materials, and advances in its measurement technique will have significant impact on materials science and related applications. Here, a photoacoustic thermorelaxation microscopy is proposed as a new noncontact method to measure the thermal diffusivity. By delivering co-focused heating/probing laser pulse pairs with tunable time delays, the sample’s in situ thermal relaxation behavior after the heating pulse excitation can be photoacoustically monitored based on the temperature-dependent property of Grueneisen parameter. We theoretically deduced the dependence of the obtained photoacoustic thermorelaxation time on the thermal diffusivity, and results coincided well with simulations. The feasibility of this method was validated by various industrial and biological samples. This method provides a new strategy for high resolution thermal diffusivity measurement with flexible measurement conditions, prefiguring great potential for material and biological applications.

Graphene-based meta-coupler for direction-controllable emission of surface plasmons

Hua Zhu, Ming Deng, Shuqi Chen, and Lin Chen

Doc ID: 365145 Received 15 Apr 2019; Accepted 09 Jun 2019; Posted 10 Jun 2019  View: PDF

Abstract: Gradient metasurfaces have offered a promising approach to achieve high-efficiency conversion between surface plasmons (SPs) and propagating waves (PWs), and hence have found numerous applications in photonics. However, the available SP-PW couplers lack flexibility for active control, which limits their use in practice. Graphene-based meta-couplers are proposed to realize dynamical SP-PW conversion by providing a tunable phase shift to the scattering SPs by means of chemical potential modulation of graphene. In-plane/out-of-plane SP-PW conversions are demonstrated with graphene ribbon/block based meta-couplers. Converting SPs to single- or two- beams of PWs with variable radiation angles is realizable by varying the chemical potential of graphene without re-optimizing the structural parameters.

Real-time Functional Photoacoustic Remote Sensing Microscopy

Kevan Bell, Parsin Haji Reza, and Roger Zemp

Doc ID: 364271 Received 04 Apr 2019; Accepted 09 Jun 2019; Posted 10 Jun 2019  View: PDF

Abstract: A fiber-tetherable non-contact photoacoustic remote sensing (PARS) microscopy system capable of multiplex functional imaging is reported. By utilizing stimulated Raman scattering within an over-pumped polarization-maintaining single-mode optical fiber, rapid pulse-to-pulse switching (500 kHz) of excitation spectral content is demonstrated and utilized as a photoacoustic excitation source. These rapid acquisitions aim to reduce motion artifacts and facilitate high frame rates appropriate for a real-time feedback to users. The system is characterized by estimating blood oxygen saturation in blood-flow phantoms and within a mouse ear in vivo.

Excitation of whispering gallery modes with a "point-and-play", fiber-based, optical nano-antenna

Jonathan Ward, Fuchuan Lei, Stephy Vincent, Pooja Gupta, Samir Mondal, Jochen Fick, and Sile Nic Chormaic

Doc ID: 364673 Received 09 Apr 2019; Accepted 09 Jun 2019; Posted 10 Jun 2019  View: PDF

Abstract: We demonstrate the excitation and detection of whispering gallery modes (WGMs) in optical microresonators using a "point-and-play", fiber-based, optical nano-antenna. The coupling mechanism is based on cavity-enhanced Rayleigh scattering. The collected spectra exhibit either Lorentzian dips, Fano shapes, or Lorentzian peaks, with a coupling efficiency around 1.8%. The spectra are characterized by the coupling gap, the polarization, and the fiber tip position. The coupling method is simple, low-cost and, most importantly, the Q-factor can be maintained at 10^8 over a wide coupling range, thereby making it particularly suitable for metrology, sensing, or cavity quantum electrodynamics (cQED) experiments.

Novel full-field micro surface profilometry using diffractive image correlation without vertical scanning

L Chen, GUO-WEI WU, and DUC TRUNG NGUYEN

Doc ID: 366973 Received 09 May 2019; Accepted 08 Jun 2019; Posted 17 Jun 2019  View: PDF

Abstract: A full-field micro profilometry involving innovative diffractive image correlation was developed for profile measurement without vertical scanning. High-speed optical inspection has become critical for confirming precise dimensions in semiconductor fabrication such as microbumping in 3-D stacked ICs and precision manufacturing. A digital micromirror device (DMD) is designed to serve as a point-light-source array in a quasi-confocal optical configuration and perform lateral scanning to minimize signal crosstalk between neighboring testing points. More importantly, multiple diffractive images are detected and measured with a pre-built depth-correlated database to extract the height information of a tested surface. A 100-nanometer repeatability can be realized in the absence of a detector pinhole and without vertical scanning, thus achieving high-speed submicrometer-scale surface profilometry.

Volumetric 3D display in real space using a diffractive lens, fast projector and polychromatic light source

Christopher Blackwell, Chi Can, Javid Khan, Xianzhong Chen, and Ian Underwood

Doc ID: 364745 Received 10 Apr 2019; Accepted 07 Jun 2019; Posted 10 Jun 2019  View: PDF

Abstract: We present a method for realising a solid-state volumetric display based on the chromatic dispersion properties of a 150 mm diffractive lens that images a series of planar patterns presented by a DMD projector. The projector is driven by a narrowband polychromatic source where the position of each image plane is defined by a distinct wavelength of light. The volumetric display system achieves 20 image planes at a volume refresh rate of 20 Hz, creating a volume of 17.2 cm³ with 13 mm of depth and a field of view (FOV) of 10º floating 145 mm above the lens in real space.

Axiparabola: a long focal depth, high resolution mirror for broadband high intensity lasers

Slava Smartsev, Clement Caizergues, Kosta Oubrerie, Julien Gautier, Jean-Philippe GODDET, Amar Tafzi, Kim Ta Phuoc, Victor Malka, and Cedric Thaury

Doc ID: 365351 Received 22 Apr 2019; Accepted 07 Jun 2019; Posted 10 Jun 2019  View: PDF

Abstract: Diffraction puts a fundamental limit to the distance over which a light beam can remain focused. For about 30 years, several techniques to overcome this limit have been demonstrated. Here, we propose a reflective optics, namely the axiparabola, which allows to extend the production of 'diffraction-free' beams to high peak power and broadband laser pulses. We first describe the properties of this aspheric optics. We then analyze and compare its performances in numerical simulations and in experiments. Finally we use it to produce a plasma wave-guide that can guide an intense laser pulse for 10 millimeters.

High-resolution nonlinear fluorescence microscopy using repetitive stimulated transition based on the saturation of stimulated emission implemented with two-color continuous-wave lasers

Fumihiro Dake and Seri Hayashi

Doc ID: 362260 Received 18 Mar 2019; Accepted 07 Jun 2019; Posted 10 Jun 2019  View: PDF

Abstract: High-resolution nonlinear fluorescence microscopy that utilizes repetitive stimulated transition due to the saturation of stimulated emission caused by two-color continuous-wave lasers was developed. The resulting nonlinear fluorescence signal, detected via the lock-in technique, is produced by the multiplicative combination of incident beams, which results in an improvement of the optical resolution. The proposed method is demonstrated to have a three-dimensional optical resolution superior to that of conventional nonlinear fluorescence microscopy. The results of biological imaging reveal the feasibility and superiority of the proposed method.

Artificial Neural Network for classification of nanoparticles shape distributions

Yehia Mansour, Yann Battie, Aotmane En Naciri, and Nouari Chaoui

Doc ID: 365589 Received 22 Apr 2019; Accepted 06 Jun 2019; Posted 10 Jun 2019  View: PDF

Abstract: A new methodology is developed to determine the shape distribution profile of gold nanoparticles (NPs) from optical spectroscopic measurements. Indeed, an artificial neural network (ANN) approach was introduced to classify Au nanoparticle (NP) shape distributions from their normalized absorption spectra. This ANN quantitatively analyzes the absorption spectra and provides the posterior probability to have a bimodal or unimodal shape distribution. Several colloidal suspensions were considered to investigate the robustness of the ANN approach. The comparison between ANN classification and TEM analysis was also given and discussed. We demonstrate that ANN classification is a suitable tool to inspect rapidly Au colloidal suspensions after their synthesis.

Projection extrapolation routine for tight frame limited-angle optical diffraction tomography

Piotr Makowski and Michał Ziemczonok

Doc ID: 366499 Received 01 May 2019; Accepted 06 Jun 2019; Posted 11 Jun 2019  View: PDF

Abstract: We propose a data-replenishment-type expansion of the modified Gerchberg-Papoulis (GP) algorithm for limited-angle optical diffraction tomography (LAODT), which prevents artifact buildup in GP reconstructions of confined bulk objects tightly fitting the active field of view (FoV) of the LAODT microscope. Objects crossing FoV borders are not considered. The method relies on a Fourier based forward projector complementary to the GP solver with no additional constraints. Fourier space regridding errors are minimized by means of 1-dimensional oversampling in axial direction, which is demonstrated to be more efficient than standard projection padding. Verification on both synthetic and experimental sinograms confirms ability of the procedure to deduce missing projection parts necessary for correct reconstruction.

Enhanced absorption in a graphene embedded 1D guided-mode-resonance structure without back-reflector and interferometrically written gratings

Pankaj Sahoo, Jian Yi Pae, and Murukeshan Matham

Doc ID: 365307 Received 17 Apr 2019; Accepted 06 Jun 2019; Posted 12 Jun 2019  View: PDF

Abstract: A theoretical model based on coupled mode theory is presented to calculate the absorption in a graphene embedded 1D guided-mode-resonance (GMR) structure that does not require a back reflector. The optimized graphene-GMR structure can absorb up to 70% of the incident light which far exceeds the already reported results without using any back-metal reflector or Bragg mirror. The theoretical analysis is valid for binary gratings and pyramidal gratings which are patterned using an interference lithography system. We experimentally validate our theoretical results and analyse the influence of the geometrical parameters to achieve critical coupling for the enhanced absorption.

Polarization-encoded field measurement in subwavelength scattering

Aristide Dogariu, Zhean Shen, and SHENGWEI cui

Doc ID: 365113 Received 15 Apr 2019; Accepted 06 Jun 2019; Posted 13 Jun 2019  View: PDF

Abstract: We demonstrate that polarization encoding provides a convenient way to realize a robust common-path interferometer for measuring both the phase and the amplitude of scattered optical fields. Moreover, for a given detector array, the design allows maximizing the interferometric visibility and, therefore, permits reaching the sensitivity limit for the field measurement. The approach is of particular interest for inefficient scattering scenarios such as subwavelength scattering.

High-efficiency Huygens’ metasurface for terahertz wave manipulation

Ruiqiang Zhao, zheng zhu, Guohua Dong, tingting Lv, Yuxiang Li, Chunying Guan, Jin-hui Shi, and Han Zhang

Doc ID: 367935 Received 20 May 2019; Accepted 06 Jun 2019; Posted 14 Jun 2019  View: PDF

Abstract: A fair amount of theoretical work has showed that Huygens’ metasurfaces well modulate electromagnetic waves by properly designing electrical impedance Zes and magnetic admittance Yms, however, transmissive Huygen's metasurface is still challenging in the THz band. In this work, a transmission-type Huygens’ metasurface with bilayer metallic patches has been proposed and theoretically demonstrated to show a reflectionless phase modulation for linearly polarized THz wave. The simulation results show that the metasurface can achieve 2π phase coverage, and importantly the phase change can be simply achieved by changing a single geometric parameter of the meta-molecule, along with similar transmission effect. We design a high-efficiency beam deflector to realize an anomalous refraction with an angle of 19.8°. The proposed metasurface will provide a simple and direct way to realize efficient THz devices for wave front manipulation.

Anomalous Optical Forces in PT-Symmetric Waveguides

Mohammad-Ali Miri, Michele Cotrufo, and Andrea Alu

Doc ID: 362412 Received 13 Mar 2019; Accepted 06 Jun 2019; Posted 17 Jun 2019  View: PDF

Abstract: Evanescently coupled passive waveguides experience optical forces of attractive or repulsive nature depending on the mode of operation. Here, we explore optical forces between parity-time-symmetric coupled waveguides, with balanced levels of gain and loss. We find that, besides the diagonal stress components that result in a pressure normal to the surface of the waveguides, this system exhibits an off-diagonal stress component that creates a shear along the propagation direction. In addition, for a critical value of balanced gain and loss, the normal pressure can be reduced to zero. These anomalous optical forces are related to the unusual power flow in coupled active-passive channels, and open interesting opportunities for microfluidics and micro-optomechanical systems.

Control of orbital angular momentum with partially coherent vortex beams

Yongtao Zhang, Yangjian Cai, and Gregory Gbur

Doc ID: 364414 Received 05 Apr 2019; Accepted 06 Jun 2019; Posted 20 Jun 2019  View: PDF

Abstract: We investigate the orbital angular momentum of partially coherent beams which are constructed by a superposition of mutually incoherent vortex modes, each mode having a different beam width and topological charge. It is shown that these simple beams nevertheless provide great flexibility in controlling orbital angular momentum through adjustment of the beam parameters, and have significant potential for particle rotation and trapping.

Terahertz generation in parallel plate waveguides activated by nonlinear metasurfaces

Symeon Sideris and Tal Ellenbogen

Doc ID: 367020 Received 10 May 2019; Accepted 05 Jun 2019; Posted 17 Jun 2019  View: PDF

Abstract: We present an extended Maxwell–Hydrodynamic model of free electron dynamics on metal–dielectric interfaces that allows to study numerically the THz emission from nonlinear metasurfaces. This model is applied on a metasurface, consisting of split ring resonators, which has been previously studied and shown to produce broadband THz radiation. Investigations of the emitted THz radiation as function of the duration of the excitationlaser reveal a tuning mechanism in terms of both spectral peak position and intensity. We use the model also to propose a new metasurface activated waveguide platform that efficiently generates THz waveguide modes.Tunability mechanisms of the generated THz are shown. Due to its unique characteristics, we believe that this new platform might play a major role in forthcoming THz applications.

Nd3+-activated CaF2 ceramic lasers

Hengjun Chen, Akio Ikesue, Hiroyuki Noto, Hiyori Uehara, Yoshimitsu Hishinuma, Takeo Muroga, and Ryo Yasuhara

Doc ID: 368153 Received 23 May 2019; Accepted 05 Jun 2019; Posted 10 Jun 2019  View: PDF

Abstract: Nd,Y:CaF2 and Nd,La:CaF2 ceramics featuring good optical quality have been fabricated by reactive sintering and hot isostatic pressing method. The transmission spectra, emission spectra, and fluorescence decay curves were measured. Lasing at 1064 nm and 1065 nm were observed in Nd,Y:CaF2 and Nd,La:CaF2, respectively, upon quasi-continuous-wave pumping by a diode laser emitting at 791 nm. This is the first demonstration of Nd3+-activated CaF2 ceramic laser to the best of our knowledge.

Frequency-modulated continuous-wave microwave generation using stabilized period-one nonlinear dynamics of semiconductor lasers

Chin-Hao Tseng, Yu-Han Hung, and Sheng-Kwang Hwang

Doc ID: 367963 Received 20 May 2019; Accepted 05 Jun 2019; Posted 06 Jun 2019  View: PDF

Abstract: Frequency-modulated continuous-wave (FMCW) microwave generation is studied using a semiconductor laser operating at stabilized period-one (P1) nonlinear dynamics when subject to comb-like (CL) optical injection. The phase locking established between the P1 dynamics and the CL optical injection not only improves the P1 oscillation stability considerably but also provides a mechanism to change the P1 oscillation frequency through varying the modulation frequency of the CL optical injection. As a result, a stable FMCW microwave at a central frequency of up to 40 GHz is generated with its frequency varying linearly, triangularly, or step-wisely over a range of 4 GHz during a repeated time period that can be reconfigured at least from 100 ns to 10 ms. This system is capable of operation up to at least 100 GHz.

Sub-Second Quantum Cascade Laser Based Infrared Spectroscopic Ellipsometry

Alexander Ebner, Robert Zimmerleiter, Christoph Cobet, Kurt Hingerl, Markus Brandstetter, and Jakob Kilgus

Doc ID: 366212 Received 01 May 2019; Accepted 05 Jun 2019; Posted 05 Jun 2019  View: PDF

Abstract: Laser-based infrared spectroscopic ellipsometry is demonstrated for the first time by applying a tunable quantum cascade laser (QCL) as mid-infrared (MIR) light source. The fast tunability of the employed QCL combined with phase modulated polarization enabled the acquisition of broadband (900 cm-1 – 1204 cm-1), high resolution (1 cm-1) ellipsometry spectra in less than 1 second. A comparison to a conventional Fourier-transform spectrometer based IR ellipsometer resulted in an improved signal-to-noise ratio (SNR) by a factor of at least 290. The developed ellipsometry setup was finally applied for real-time monitoring of molecular reorientation during the stretching process of an anisotropic polypropylene film, thereby illustrating the advantage of sub-second time resolution. The developed method exceeds existing instrumentation by its fast acquisition and high SNR, which could open up a set of new applications of spectroscopic ellipsometry such as ellipsometric inline process monitoring and quality control.

A statistical theory of the polarization on the Poincaré sphere

Rafael Torres and Karol Salazar-Ariza

Doc ID: 367407 Received 13 May 2019; Accepted 04 Jun 2019; Posted 04 Jun 2019  View: PDF

Abstract: The random nature of light emitters requires that the theory to study polarization must adopt a statistical approach. Although the Stokes parameters are proposed in this sense, these are implemented as temporal averages, appealing to an ergodic hypothesis, without discussing which probability distributions are treated. Therefore, here the polarization dynamics on the Poincaré sphere of random light sources, whose phases and amplitudes of the electric fields are statistically independent, is described through the von Mises-Fisher distribution. This allowed us to relate the degree of polarization and the normalized Stokes parameters with the concentration parameter and the mean direction of the von Mises-Fisher distribution. Also, it is found that their marginal distributions have the same statistically behavior of the Eliyahu-Brosseau distribution.

Fraunhofer Diffraction and the State of Polarization ofPartially Coherent Electromagnetic Beams

yangyundou wang, shenggang yan, Xiaofei Li, Xianlong Liu, Yang Jiancai, Govind Agrawal, and Taco Visser

Doc ID: 368716 Received 31 May 2019; Accepted 04 Jun 2019; Posted 06 Jun 2019  View: PDF

Abstract: We generalize the concept of Fraunhofer diffraction to partially coherent electromagnetic beams and show how the state of polarization is affected by a circular aperture. It is illustrated that the far-zone properties of a random beam can be tuned by varying the aperture radius. We find that even an incident beam that is completely unpolarized can sometimes produce a field thatis highly polarized.

Reducing the phase noise in diode lasers

Raul Rincon Celis and Marcelo Martinelli

Doc ID: 363100 Received 25 Mar 2019; Accepted 04 Jun 2019; Posted 10 Jun 2019  View: PDF

Abstract: Diode lasers are widely used in atomic physics given its narrow linewidth and wavelength tunability. Nevertheless, although they present a low noise for their intensity, their excessive noise in the phase limits their application in quantum optics. Looking for the reduction of this phase noise, we built and characterize a ring laser, using a semiconductor tapered amplifier as the gain medium. We were able to reduce the phase noise of a diode laser to a factor of 10 above shot noise level, bringing it closer to a useful coherent state for applications in quantum information.

Background-free two-photon fluorescence readout via a three-photon charge-state modulation of nitrogenvacancy centers in diamond

Ilya Fedotov and Aleksei Zheltikov

Doc ID: 364949 Received 11 Apr 2019; Accepted 04 Jun 2019; Posted 04 Jun 2019  View: PDF

Abstract: We demonstrate that a background-free readout of two-photon fluorescence from NV centers in a strongly fluorescing environment can be accomplished by all-optical means, via a multiphoton charge-state modulation of nitrogen–vacancy (NV) centers in a mixture of negatively charged and neutral NV centers. A 100-fs, 1060-nm output of an ytterbium fiber laser is ideally suited for this modality of multiphoton microscopy, providing, as our experiments show, an efficient two-photon excitation of both NV- and NV0 charge states, but keeping the nonlinearity of n-photon ionization needed for NV-/NV0 charge-state modulation to a minimum, n = 3.

Design of InSb thermoradiative system for harvesting low-grade waste heat

Xin Zhang, Yee Sin Ang, Jincan Chen, and Lay Kee Ang

Doc ID: 367221 Received 13 May 2019; Accepted 04 Jun 2019; Posted 06 Jun 2019  View: PDF

Abstract: We propose a thin-film InSb-based thermoradiative system (TRS) and to access its performance characteristics by using parametric design at low-grade waste heat. Our results predict that the 50nm-thick InSb TRS operating with a hot (cold) source at 500K (300K) may yield a power density of 113 Wm-2 and an efficiency limit of 10.5%. We identify the dominant loss contributors limiting the power generation and conversion efficiency. To enhance the system performance, more efforts should be paid to reduce layer thickness, enhance optical radiation, improve surface passivation, and fabricate an Ag back reflective mirror and an optical filter for frequency-dependent photons recycling. This letter provides new insights for optimal designs and energy loss mechanisms, thus paving a route towards the development of practical TRS at a low temperature around 500K.

Splitting spoof surface plasmon polaritons to different directions with high efficiency in ultra-wideband frequencies

Jun Wang, Lei Zhao, zhangcheng hao, Xiaopeng Shen, and Tie Jun Cui

Doc ID: 365878 Received 24 Apr 2019; Accepted 03 Jun 2019; Posted 10 Jun 2019  View: PDF

Abstract: An efficient method to split spoof surface plasmon polaritons (SSPPs) to different directions is proposed by designing a low-loss SSPP waveguide in an ultrawide frequency band. For this purpose, a coplanar waveguide (CPW)-based SSPP structure with double-row hole arrays etched on its middle line is first studied, which can be easily used to split the SSPP waves. Based on this method, a Y-shaped -3 dB SSPP power divider and its application on Mach-Zehnder interferometer are presented. The experiment demonstrates that the proposed method splits the SSPP waves to different directions effectively in ultrawide frequencies (from 2.5-39.7 GHz) with good isolations, indicating that the proposed SSPP power divider can have a good application on Mach-Zehnder interferometer and may advance a big step towards other future applications in plasmonic integrated circuits.

Digital four-step phase shifting technique from a single fringe pattern using Riesz transform

Yassine Tounsi, Manoj Kumar, Ahmed Siari, Fernando Mendoza-Santoyo, ABDELKRIM NASSIM, and Osamu Matoba

Doc ID: 366679 Received 02 May 2019; Accepted 03 Jun 2019; Posted 10 Jun 2019  View: PDF

Abstract: A digital four-step phase-shifting (D4-PS) method for obtaining the optical phase distribution from a single fringe pattern is proposed in this Letter. By computing the first, second and third order Riesz transform components for a given fringe pattern, three π/2 phase shifted fringe patterns are generated from the obtained Riesz components, and finally, the wrapped phase map is extracted. The validity of the proposed method is demonstrated on both the simulated and experimentally obtained fringe patterns. The performance of the proposed method is evaluated by using the image quality index and edge preservation index. Further, the performance of the proposed method is tested on speckled correlation fringes obtained from digital speckle pattern interferometry (DSPI), and the resulting phase from the proposed method is compared with the phase obtained from three experimentally recorded phase shifted fringe patterns. The obtained results reveal that the proposed method provides a simple and robust solution for optical phase extraction from a single fringe pattern with good accuracy, and therefore, making it suitable for real-time measurement applications.

Rabi-like oscillation of photonic topological val-ley Hall edge states

Hua Zhong, Yaroslav Kartashov, Yiqi Zhang, Daohong song, Yanpeng Zhang, fuli li, and Zhigang Chen

Doc ID: 366049 Received 25 Apr 2019; Accepted 03 Jun 2019; Posted 06 Jun 2019  View: PDF

Abstract: We investigate Rabi-like oscillations of topological valley Hall edge states by introducing two zigzag domain walls in an inversion-symmetry-breaking honeycomb photonic lattice. Such resonant oscillations are stimulated by weak periodic modulation of the lattice depth along the propagation direction that does not affect the overall symmetry and the band topology of the lattice. Oscillations are accompanied by periodic switching between edge states with the same Bloch momentum, but located at different domain walls. Switching period and efficiency are the nonmono-tonic functions of the Bloch momentum in the Brillouin zone. We discuss how efficiency of this resonant process depends on detuning of modulation frequency from reso-nant value. Switching of nonlinear edge states is also briefly discussed. Our work brings about an effective approach to accomplish resonant oscillations of the valley Hall edge states in time-reversal-invariant topological in-sulators.

Freeform off-axis optical system with multiple performance settings integrated

Ruirui Tang, Guofan Jin, and Jun Zhu

Doc ID: 361283 Received 28 Feb 2019; Accepted 03 Jun 2019; Posted 04 Jun 2019  View: PDF

Abstract: Freeform optical surfaces make it possible and feasible to design systems with novel functions. In this letter, a new kind of freeform system with multiple performance settings integrated is proposed. The system can operate with different performance settings suited for different imaging demands. A movable aperture stop is used in the system for switching between the working areas suited for different performance settings. A construction method for integrated freeform surfaces is proposed herein, which considers multiple object–image relationships simultaneously. By this method, three integrated freeform systems were designed with different novel functions. This work adds more variety to the design of freeform off-axis systems.

Modelling and experimental performance analysis of a novel heating system and its application to glass hot embossing technology

Lihua Li, Ming Kit CHAN, WB Lee, William Ng, and Kin Leung CHAN

Doc ID: 368057 Received 21 May 2019; Accepted 03 Jun 2019; Posted 12 Jun 2019  View: PDF

Abstract: Traditional glass molding involves infra-red heating, however the thermal cycle time is long. A molding technique based on three-dimensional carbide-bonded graphene (CBG) has been developed to mold boron silicon glass. This CBG coating on a wafer silicon die can serve as a thin-film resistance heater to heat up the sample surface very rapidly with a relatively low applied voltage. To improve the precision temperature control in hot embossing so as to enhance the process quality, a heating system with lower energy consumption, shorter cycle time and much more precision control is proposed. We have used COMSOL to simulate the whole heating process and the heating behavior of a CBG coated silicon wafer was experimentally investigated. The results showed that the repeatability of the heating system is stable and it is suitable for precision glass hot embossing. Finally, an example of a precisely fabricated microlens array (Schott P-SK57) is embossed by using this novel heating system.

Resonance-free Ultraviolet Metaoptics via Photon Nanosieves

Juan Li, guangyuan si, Hong Liu, Jiao Lin, Jinghua Teng, and Kun Huang

Doc ID: 365010 Received 16 Apr 2019; Accepted 03 Jun 2019; Posted 13 Jun 2019  View: PDF

Abstract: Ultraviolet (UV) light with high-energy photons is widely used in various areas such as nano-lithography, biology and photoemission spectroscopy. The flexible control over its amplitude and phase is a longstanding problem due to the strong absorption from most materials. Here, we propose a nano-aperture platform to control the amplitude and phase of UV light and experimentally demonstrate amplitude- and phase-type holograms at the wavelength of 355nm. In principle, the nano-apertures etched on a metal film can be filled in vacuum so that no material issue is involved in this configuration, allowing us to manipulate the UV light through the geometry of nano-apertures even when the plasmonic resonances are absent. A binary-amplitude nanosieve is used to reconstruct three holographic images at different cut-planes by tuning the constructive interference elaborately. Meanwhile, the rectangle nano-apertures are employed to demonstrate the UV holograms with geometric phase that is controlled by the orientation of the nano-apertures. This platform could be extended to other UV regions.

Fiber-based platform for synchronous imaging of endogenous and exogenous fluorescence of biological tissue

Alba Alfonso Garcia, Cai Li, Julien Bec, Diego Yankelevich, Laura Marcu, and Benjamin Sherlock

Doc ID: 366040 Received 25 Apr 2019; Accepted 01 Jun 2019; Posted 06 Jun 2019  View: PDF

Abstract: Endogenous and exogenous fluorescence emission from biological samples encodes complimentary information. Here we report first results from an optical imaging platform with interleaved excitation and detection of exogenous and endogenous fluorescence from tissue samples using a single flexible multimode fiber that delivers the excitation beam and collects the emitted light. A custom built reflective optical chopper wheel with synchronized rotation temporally multiplexes an autofluorescence lifetime imaging apparatus with an intensity-based fluorescence module tailored to imaging green fluorescent protein. We demonstrate the functionality of such platform imaging dyes of varying fluorescence signatures and resolving cellularized areas on bio-engineered tissue constructs.

Encoding lenses with focal lengths lower than the Nyquist limit using high phase-modulation displays

Benjamin Gutierrez, Jeffrey Davis, Ignacio Moreno, and Don Cottrell

Doc ID: 363380 Received 27 Mar 2019; Accepted 31 May 2019; Posted 10 Jun 2019  View: PDF

Abstract: Liquid crystal displays allow the easy implementation of diffractive optical elements. However, the shortest focal lengths for lenses are limited by Nyquist conditions. In this work, we show that focal lengths much lower than this Nyquist limit can be encoded onto devices having a large phase-dynamic range. Experimental results are included with a display showing 10π phase modulation reducing the Nyquist limit by a factor of about 1/10.

Broadband and robust adiabatic second harmonic generation by temperature gradient in birefringently phase matched lithium triborate crystal.

Eyal Rozenberg and Ady Arie

Doc ID: 366406 Received 30 Apr 2019; Accepted 31 May 2019; Posted 31 May 2019  View: PDF

Abstract: Phase matched nonlinear processes exhibits a tradeoff between the conversion efficiency and the acceptance bandwidth. Adiabatic nonlinear processes, in which the phase mismatch varies slowly along the interaction length, enable to overcome this tradeoff, allowing an efficient frequency conversion with broad spectral and thermal bandwidths. Up till now, the variation in the phase mismatch condition was mainly based on quasi phase matching in ferroelectric crystals. However, this solution is limited to low power sources. Here, instead, we study adiabatic second harmonic in birefringently phase matched lithium triborate crystal, enabling to handle much higher power levels. The variation in the phase mismatch is achieved by inducing a temperature gradient along the crystal. By using a 50 mm long crystal, the adiabatic process provided a temperature bandwidth of 18$^{\circ}$C, 5.4 times wider than what is achieved when the same crystal is held at the fixed phase matching temperature. The conversion efficiency exceeded 60\% for a 0.9 milliJoule pump pulse.

Ultrafast and ultrahigh-resolution optical vector analysis using linearly frequency-modulated waveform and dechirp processing

Li Shupeng, Min Xue, Ting Qing, Changyuan Yu, Lugang Wu, and Shilong Pan

Doc ID: 365836 Received 24 Apr 2019; Accepted 30 May 2019; Posted 04 Jun 2019  View: PDF

Abstract: We propose and experimentally demonstrate an ultrafast and ultrahigh-resolution optical vector analyzer (OVA) using linearly frequency-modulated (LFM) waveform and dechirp processing. An optical LFM signal, achieved by modulating an electrical LFM signal on an optical carrier via carrier-suppressed optical single-sideband (OSSB) modulation, is separated into two portions. One portion (denoted as the reference signal) directly goes through the reference path, and the other (denoted as the probe signal) undergoes magnitude and phase changes by an optical device under test (DUT) in the measurement path. After balanced photodetection, the reference signal and the probe signal are mixed to perform dechirp operation. A relatively low-frequency electrical signal is generated, which can be sampled by a low-speed ADC. As a result, the frequency responses of the DUT can be extracted at a high speed by post digital signal processing. Thanks to the large chirp rate of the electrical LFM signal and the dechirp processing, the proposed LFM-based OVA enables ultrafast measurement speed and ultrahigh frequency resolution. An experiment is performed, in which a narrowband tunable optical filter is characterized. The measurement speed reaches 1 ns/point, and the frequency resolution is 1.6 MHz.

Loss reduction in electro-mechanically-tunable microring cavities

Marcel Pruessner, Doewon Park, Brian Roxworthy, Dmitry Kozak, Todd Stievater, Nathan Tyndall, and William Rabinovich

Doc ID: 366228 Received 29 Apr 2019; Accepted 30 May 2019; Posted 31 May 2019  View: PDF

Abstract: Nanophotonic structures coupled with mechanics enable large effective index perturbation. To date, however, the relation between index tuning and induced optical loss has not been considered in detail. In this work we present an in depth study of optical loss mechanisms in an electro-mechanically-tunable waveguide filter. Gradient electric forces modify the coupling between a microring optical cavity and a suspended micromechanical (MEMS) perturber resulting in a measured tuning greater than one free-spectral range (FSR) and an effective index tuning of 3x10-². We examine various loss contributions and find, for certain conditions, a surprising reduction in loss with greater MEMS-induced mode perturbation. Modeling confirms the device behavior and loss mitigation is discussed.

Time-resolved dual-comb measurement of number density and temperature in a laser-induced plasma

Yu Zhang, Caroline Lecaplain, REAGAN WEEKS, Jeremy Yeak, Sivanandan Harilal, Mark Phillips, and R. Jason Jones

Doc ID: 364639 Received 07 May 2019; Accepted 28 May 2019; Posted 31 May 2019  View: PDF

Abstract: We utilize time-resolved dual-comb spectroscopy to measure the temporal evolution of the population number densities and absorption excitation temperature of Fe in a laser induced plasma. The spectrum of three excited-state transitions of Fe around 533 nm are simultaneously easured at different time delays following laser ablation of a stainless steel sample. This work probes late-time behavior of laser-induced ablation plumes during plasma cooling. The high spectral resolution and broad spectral coverage of the dual-comb technique, combined with the time-resolved measurement capability shown here, will aid in the characterization of laser induced plasmas, including species identification and molecule and particle formation that can occur at later times in the plasma evolution.

Diode-pumped 640-nm Pr:YLF regenerative laser pulse amplifier

Naoto Sugiyama, Shogo Fujita, Yusaku Hara, Hiroki Tanaka, and Fumihiko Kannari

Doc ID: 365808 Received 26 Apr 2019; Accepted 28 May 2019; Posted 10 Jun 2019  View: PDF

Abstract: We demonstrated regenerative laser pulse amplification at 640 nm for the first time with a mode-locked Pr3+-doped LiYF4 (Pr3+:YLF) oscillator as a picosecond seed pulse. A regenerative amplifier with a Pr3+:YLF crystal was continuously pumped by a multimode InGaN diode laser. At an absorbed pump power of 3.1 W, we obtained amplified pulse energy of 13 μJ at 10 kHz with an excellent spatial beam quality of M2=1, demonstrated second harmonic generation, and obtained a 320-nm pulse energy of 1.7 μJ.

Common-path off-axis incoherent Fourier holography with a maximum overlapping interference area

Cuong Nguyen and Hyuk-Sang Kwon

Doc ID: 362433 Received 14 Mar 2019; Accepted 25 May 2019; Posted 28 May 2019  View: PDF

Abstract: In this letter, we present a new method for recording spatially incoherent common-path off-axis Fourier holograms. This method records the three-dimensional (3D) information of an object into a Fourier hologram without the need of any mechanical scanning with incoherent illumination. The proposed setup consists of two gratings to form a common-path configuration, two customized cells to create a rotational and radial shearing interferometer, and second axially shifted grating to build an off-axis geometry. A lens is used to combine two beams that generate the maximum overlapping area at the hologram plane. Proof-of-concept experiments confirmed the ability of such system to achieve the maximum overlapping interference area, the stability of system against the vibration of surrounding environment, the numerical reconstruction using only one Fast Fourier Transform (FFT), and the 3D capability to capture a 3D object illuminated by an LED light.

Microfabrication of axicons by glass blowing at a wafer-level

José Carrión Pérez, Jorge Albero, Maciej Baranski, Christophe Gorecki, and Nicolas Passilly

Doc ID: 365462 Received 19 Apr 2019; Accepted 24 May 2019; Posted 28 May 2019  View: PDF

Abstract: This letter reports on the generation of glass-based axicons realized at wafer-level by means of microfabrication. The technique is based on micro glass blowing allowing parallel fabrication of numerous components at a time. Blowing is achieved thanks to cavities containing a gas which expands when the wafer stack is introduced in a furnace. Such cavities, generated in a silicon wafer and sealed by a bonded glass wafer, act as pistons pushing locally the other side of the glass wafer where the micro-optical component profile emerges. After cavities removal by polishing, it is shown that such component produces nondiffracting Bessel beams.

Low-loss high-Q silicon-rich silicon nitride microresonators for Kerr nonlinear optics

Zhichao Ye, Attila Fulop, Óskar Helgason, Peter Andrekson, and Victor Torres Company

Doc ID: 365031 Received 12 Apr 2019; Accepted 24 May 2019; Posted 03 Jun 2019  View: PDF

Abstract: Silicon nitride is a dielectric material widely used for applications in linear and nonlinear optics. It has an ultra-broad transparency window, low intrinsic loss and a refractive index that allows for moderate optical field confinement in waveguides. The chemical composition of this material can be precisely set during the fabrication process, leading to an extra degree of freedom for tailoring the optical and mechanical properties of photonic chips. Silicon-rich silicon nitride waveguides are appealing for nonlinear optics because they have higher nonlinear Kerr coefficient and refractive index than what is possible with stoichiometric silicon nitride. This is a direct consequence of the increased silicon content. However, silicon-rich silicon nitride waveguides typically display higher absorption losses. In this Letter, we report low loss (~0.4 dB/cm) silicon-rich silicon nitride waveguides. The structures feature high optical confinement and can be engineered with low anomalous dispersion. We find an optimum silicon composition that overcomes optical losses associated to N-H bonds in the telecom band through an annealing process. Based on this technology, we successfully fabricate microresonators with mean quality factors (Q) ~ 800 000 in the C and L bands. Broadband coherent microresonator frequency combs are generated in this platform, indicating its potential for efficient Kerr nonlinear optics.

Compact Pico-meter Scale Interferometer using Twisted Light

Gyanendra Yadav and Gopal Verma

Doc ID: 358003 Received 17 Jan 2019; Accepted 02 Mar 2019; Posted 19 Jun 2019  View: PDF

Abstract: We propose a simple compact interferometer using twisted light to detect pico-meter displacement on a solid or liquid surface. The heart of the interferometer lies in producing daisy petal pattern formed by interference between two oppositely charged twisted beams. The sample being probed is an active component of the interferometer. By analyzing the rotation of petal pattern, caused due to the relative displacement between the cylindrical lens (CL) and solid/liquid surface, we exhibit pico-meter resolution in displacement measurements. Remarkably, we explore the significance of radial quantum number in the measurement of surface displacement and surface tilt angle. We also investigate the arbitrary surface deformation profile with similar precision by modifying the set-up. We perform simulations in realistic experimental settings and show that they are in excellent agreement with the predictions of analytic expressions. The proposed set-up can be further miniaturized by small focal length CL and will open route for tremendous applications in pico-meter scale displacement measurement of a solid or liquid interface by various excitation.

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