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Real-time, in-situ probing of Gamma radiation damage with packaged integrated photonic chips

Qingyang Du, Jerome Michon, Bingzhao Li, Derek Kita, Danhao Ma, Haijie Zuo, Shaoliang Yu, Tian Gu, Anuradha Agarwal, Mo Li, and Juejun Hu

DOI: 10.1364/PRJ.379019 Received 02 Oct 2019; Accepted 03 Dec 2019; Posted 04 Dec 2019  View: PDF

Abstract: Integrated photonics is poised to become a mainstream solution for high-speed data communications and sensing in harsh radiation environments such as outer space, high-energy physics (HEP) facilities, nuclear power plants, and test fusion reactors. Understanding the impact of radiation damage in optical materials and devices is thus a prerequisite to building radiation-hard photonic systems for these applications. In this paper, we report real-time, in-situ analysis of radiation damage in integrated photonic devices. The devices, integrated with an optical fiber array package and a baseline-correction temperature sensor, can be remotely interrogated while exposed to ionizing radiation over a long period without compromising their structural and optical integrity. We also introduce a method to deconvolve the radiation damage responses from different constituent materials in a device. The approach was implemented to quantify Gamma radiation damage and post-radiation relaxation behavior of SiO2-cladded SiC photonic devices. Our findings suggest that densification induced by Compton scattering displacement defects is the primary mechanism for the observed index change in SiC. Additionally, post-radiation relaxation in amorphous SiC does not restore the original pre-irradiated structural state of the material. Our results further point to the potential of realizing radiation-hard photonic device designs taking advantage of the opposite signs of radiation-induced index changes in SiC and SiO2.

High energy all-fiber gain-switched thulium-doped fiber laser for volumetric photoacoustic imaging of lipids

Can Li, Jiawei Shi, Xiatian Wang, boquan wang, Xiaojing Gong, Liang Song, and Kenneth Kin-Yip Wong

DOI: 10.1364/PRJ.379882 Received 07 Oct 2019; Accepted 03 Dec 2019; Posted 04 Dec 2019  View: PDF

Abstract: We demonstrate a high-energy all-fiber short wavelength gain-switched thulium-doped fiber laser for volumetric photoacoustic (PA) imaging of lipids. The laser cavity is constructed by embedding a short piece of gain fiber between a pair of fiber Bragg grating (FBG). Through utilizing three pairs of FBG with operation wavelength at 1700 nm, 1725 nm and 1750 nm, respectively, three similar lasers are realized with a cavity length of around 25 cm. Under a maximum pump energy of 300 μJ at 1560 nm, laser pulse energies of 58.2 μJ, 66.8 μJ and 75.3 μJ are respectively achieved with a minimum pulse width of <16.7 ns at a repetition rate of 10 kHz. Volumetric imaging of lipids is validated through scanning a piece of fatty beef with a PAM system incorporated with the newly developed source, and a lateral resolution of 18.8 μm and an axial resolution of 172.9 μm are achieved. Moreover, the higher shooting speed of the developed source can potentially allow for increasing at twice the frame rate of current intravascular PA imaging.

Distributed curvature sensing based on bending loss resistant ring-core fiber

li shen, Hao Wu, Can Zhao, Lei Shen, Rui Zhang, Weijun Tong, Songnian Fu, and Ming Tang

DOI: 10.1364/PRJ.379178 Received 02 Oct 2019; Accepted 28 Nov 2019; Posted 04 Dec 2019  View: PDF

Abstract: A theoretical and experimental study on curvature sensing using Brillouin optical time-domain analyzer (BOTDA) based on the ring-core fiber (RCF) is reported. Brillouin gain spectrum (BGS) of the RCF is investigated, and Brillouin frequency shift (BFS) dependence on temperature and strain is calibrated. We theoretically analyze the fiber bending induced BFS and peak Brillouin gain variation for the RCF through a numerical simulation method, and the RCF is revealed to have a high curvature sensitivity. Distributed curvature sensing is successfully demonstrated with the bending radius ranging from 0.5 cm to 1.5 cm, corresponding to BFS variation from 32.90 MHz to 7.81 MHz. The RCF takes the advantage of great bending loss resistance and the maximum macro-bending loss at the extreme bending radius of 0.5 cm is less than 0.01 dB/turn. Besides, the peak Brillouin gain of the RCF is discovered to vary significantly in response to fiber bending, which is expected to be another parameter for distributed curvature determination. The results imply that the RCF is a promising candidate for highly sensitive distributed curvature measurement, especially with sharp bending circumstances.

Strong mechanical squeezing in optomechanical system based on Lyapunov control

Biao Xiong, Xun Li, Shi-Lei Chao, Zhen Yang, Wen-Zhao Zhang, Weiping Zhang, and Ling Zhou

Doc ID: 373535 Received 24 Jul 2019; Accepted 26 Nov 2019; Posted 27 Nov 2019  View: PDF

Abstract: We propose a scheme to generate the strong squeezing of mechanical oscillator in an optomechanical system through Lyapunov control. A frequency modulation of mechanical oscillator is designed via Lyapunov control method. We show that the variance of the mechanical position decreases with time evolution, which results in the strong mechanical squeezing. What's more, the squeezing is largely immune to the thermal noise so that we can obtain squeezing beyond the 3-dB limit even at room temperature.

Thermometry strategy developed based on fluorescence contrast driven by varying excitations in codoped LiNbO₃

Siwei Long, Shaopeng Lin, Decai Ma, Yunzhong Zhu, Huashan Li, and Biao Wang

Doc ID: 373633 Received 26 Jul 2019; Accepted 26 Nov 2019; Posted 27 Nov 2019  View: PDF

Abstract: We proposed a novel optical thermometry strategy (FIR-Ex) based on the fluorescence intensity ratio (FIR) between two radiations associated with the same emission peak but different excitation wavelengths, in contrast to the traditional approach (FIR-Em) that depends on the FIR at varying emission wavelengths. The temperature dependent FIR within the FIR-Ex strategy arises from the different charge/energy evolution routes, rather than the distribution of thermally coupled levels within the FIR-Em strategy. Considerable diversity in thermal behaviors and luminescence mechanisms were demonstrated by analyzing the 618 nm red emission in Pr³+ doped congruent LiNbO₃ (Pr:CLN) under 360 nm and 463 nm excitations. The temperature sensitivity was further improved via Mg²+ codoping due to the optimization of charge dynamics and energy transfer processes. Given its wide detection scope, relatively high absolute sensitivity at low temperature, and high tunability of temperature sensitivity, the FIR-Ex strategy is promising for developing optical temperature sensing materials with high performance.

Microcrystals Modulated Exciton-Polariton Emissions from Single ZnO@ZnO:Ga Microwire

Mingming Jiang, Wangqi Mao, Jiaolong Ji, Peng Wan, Xiangbo Zhou, and Caixia Kan

Doc ID: 374101 Received 30 Jul 2019; Accepted 25 Nov 2019; Posted 27 Nov 2019  View: PDF

Abstract: Due to the outstanding surface-to-volume ratio, highly smooth surface and well-defined crystal boundary, semiconducting micro/nanocrystals have been utilized as pivotal platform to fabricate multifunctional optoelectronic devices, such as super resolution imaging, solar concentrators, photodetectors, light-emitting diodes (LEDs), lasers, etc. Especially, the micro/nanocrystal being foreseen as the key elements can be employed to tailor the fundamental optical and electronic transport properties of the integrated hetero/homostructures. Herein, ZnO microcrystals decorated pre-synthesized Ga-doped ZnO microwire (ZnO@ZnO:Ga MW) was prepared. The single ZnO@ZnO:Ga MW can be utilized to construct optically pumped Fabry-Perot (F-P) mode microlasers, with the dominating lasing peaks centered in the violet spectral region. In particular, stabilized exciton-polariton emissions from single ZnO@ZnO:Ga MW based heterojunction diode can also be realized. The deposited ZnO microcrystals can facilitate the strong coupling of F-P optical modes with excitons, leading to the formation of exciton-polariton features in the ZnO@ZnO:Ga MW. Therefore, it can be anticipated that the waveguiding lighting behavior and energy-band alignment of ZnO microcrystals sheathed ZnO:Ga MW radial structures are extremely attractive for potential application that hammer at semiconducting microstructures based optoelectronic devices, such as micro-LEDs, laser microcavities, waveguides, photodetectors, etc.

Erbium-doped TeO2-coated Si3N4 waveguide amplifiers with 5 dB net gain

Henry Frankis, Hamidu M. Mbonde, Dawson Bonneville, Chenglin Zhang, Richard Mateman, Arne Leinse, and Jonathan Bradley

Doc ID: 379031 Received 27 Sep 2019; Accepted 25 Nov 2019; Posted 27 Nov 2019  View: PDF

Abstract: We demonstrate 5 dB net gain in an erbium-doped tellurium-oxide-coated silicon-nitride waveguide . The amplifier design leverages the high refractive index and high gain in erbium-doped tellurite glass and ultra-low losses and mature, reliable and low cost fabrication methods of silicon nitride waveguide technology. We show that the waveguide platform demonstrates low background propagation losses of 0.25 dB/cm based on a ring resonator device with a Q factor of 1.3×10⁶ at 1640 nm. We measure 5 dB peak net gain at 1558 nm and > 3 dB of net gain across the C-band in a 6.7-cm-long waveguide for 35 mW of launched 1480 nm pump power. Gain per unit length of 1.7 and 1.4 dB/cm is measured in a 2.2-cm-long waveguide for 980 and 1480 nm pump wavelengths, respectively. These results demonstrate a promising approach for the monolithic integration of compact erbium-doped waveguide amplifiers on silicon nitride chips and within silicon-based photonic integrated circuits.

Quantum Nonreciprocality in Quadratic Optomechanics

xun wei xu, Yanjun Zhao, Hui Wang, Hui Jing, and Aixi Chen

Doc ID: 371416 Received 02 Jul 2019; Accepted 25 Nov 2019; Posted 27 Nov 2019  View: PDF

Abstract: We propose to achieve nonreciprocal quantum control of photons in quadratic optomechanical (QOM) system based on directional nonlinear interactions. We show that by optically pumping the QOM system in one side, an effective QOM coupling can be enhanced significantly in that side, but not for the other side. This, contrary to the intuitive picture, allows the emergence of nonreciprocal photon blockade in such optomechanical devices with weak single-photon QOM coupling. Our proposal opens up the prospect of exploring and utilizing quantum nonreciprocal optomechanics, with applications ranging from single-photon nonreciprocal devices to on-chip chiral quantum engineering.

Broadband on-chip photonic spin Hall element via inverse design

Zhenwei Xie, Ting Lei, Haodong Qiu, Zecen Zhang, Hong Wang, and Xiaocong Yuan

Doc ID: 374260 Received 31 Jul 2019; Accepted 20 Nov 2019; Posted 22 Nov 2019  View: PDF

Abstract: The photonic spin Hall effect plays an important role in photonic information technologies, especially in on-chip spin Hall devices. However, conventional devices suffer from low efficiency or narrow bandwidth, which prevents their practical application. Here, we introduce a spin Hall device using inverse design to achieve both high efficiency and broadband. Spin-dependent light separation is enabled by a 2.4-μm circular device with 100-nm pixels. The photonic spin Hall element is fabricated on silicon on an insulator wafer compatible with a standard integrated photonic circuit. The spin light is detected and emitted with an efficiency of up to 22% and 35%, respectively, over a 200-nm bandwidth at optical wavelength. The inversely designed spin Hall device will greatly benefit optical computing, optical sensing, optical communications, and other ultrafast or broadband photonic spin-related applications.

Ultra-fast fiber lasers mode-locked by 2D materials: review and prospect

Tian Jiang, Ke Yin, Wang Cong, Jie You, Hao Ouyang, runlin miao, chenxi zhang, Ke We, Han Li, Haitao Chen, Renyan Zhang, Xin Zheng, Zhongjie Xu, Xiang'ai Cheng, and Han Zhang

Doc ID: 365231 Received 16 Apr 2019; Accepted 19 Nov 2019; Posted 27 Nov 2019  View: PDF

Abstract: The year 2019 marks the tenth anniversary of the first report of ultra-fast fiber laser mode-locked by graphene. This result has an important impact on ultra-fast laser optics and continues to broaden new horizons. Herein, we mainly review the linear and nonlinear photonic properties of 2D materials, as well as their nonlinear applications in efficient passive mode-locking devices and ultra-fast fiber lasers. Initial works and significant progresses in this field, as well as new insights and challenges of 2D materials for ultra-fast fiber lasers, are reviewed and analyzed.

Fe3O4 nanoparticles as a saturable absorber for tunable Q-switched dysprosium laser around 3 μm

Jian Yang, Jiyi Hu, Hongyu Luo, Jianfeng Li, Jishu Liu, Xiaohui Li, and Yong Liu

Doc ID: 378727 Received 30 Sep 2019; Accepted 18 Nov 2019; Posted 19 Nov 2019  View: PDF

Abstract: We demonstrate for the first time to our knowledge the use of Fe3O4 nanoparticles for Q-switching a tunable mid-infrared (Mid-IR) Dy3+-doped ZBLAN fiber laser around 3 μm. The Q-switcher was fabricated by depositing the prepared Fe3O4 nanoparticles solution onto an Au mirror. Its nonlinear optical response was characterized using a mode locked Ho3+/Pr3+-codoped ZBLAN fiber laser at 2.87 μm, and showed a modulation depth of 11.9% as well as a saturation intensity of 1.44 MW/cm2. Inserting the device into a tunable Dy3+-doped ZBLAN fiber laser, stable Q-switched pulses within the tunable range of 2812.4~3031.6 nm were obtained. When tuning the wavelength to 2931.2 nm, a maximum Q-switching output power of 111.0 mW was achieved with a repetition rate of 1 .0 kHz and a pulse width of 1.25 μs. The corresponding pulse energy was 0.90 μJ. This demonstration suggests that Fe3O4 nanoparticles are a promising broadband saturable absorption material for mid-infrared operation.

High-Q surface electromagnetic wave resonance excitation in magneto-photonic crystals for super-sensitive detection of weak light absorption in near-IR

Olga Borovkova, Daria Ignatyeva, Alina Karabchevsky, Serguei Sekatski, and Vladimir Belotelov

Doc ID: 375736 Received 20 Aug 2019; Accepted 16 Nov 2019; Posted 19 Nov 2019  View: PDF

Abstract: Mid-infrared spectrum can be recorded from almost any material making the mid-infrared spectroscopy an extremely important and widely used sample characterization and analytical technique. However, sensitivity photoconductive detectors operate primarily in the near-infrared (NIR) but not in the mid-infrared making the NIR more favorable for accurate spectral analysis. Although absorption cross-section of vibrational modes in near-infrared is orders of magnitude smaller compared to the fundamental vibrations in mid-infrared, different concepts were proposed to increase the detectability of weak molecular transitions overtones. Yet, the contribution of magneto-photonic structures in near-infrared absorption effect has never been explored so far. Here we propose high-Q magneto-photonic structures for a super-sensitive detection of weak absorption resonances in near-infrared. We analyze the contributions of both magnetic and non-magnetic photonic crystal (PC) configurations to the detection of weak molecular transitions overtones. Our results constitute an important step towards development of highly sensitive spectroscopic tools based on high-Q magneto-photonic sensors.

Ultra-broadband, few cycle pulses directly from a Mamyshev fiber oscillator

Chunyang Ma, Ankita Khanolkar, Yimin Zang, and Andy Chong

Doc ID: 377733 Received 13 Sep 2019; Accepted 13 Nov 2019; Posted 15 Nov 2019  View: PDF

Abstract: While the performance of mode-locked fiber lasers has been improved significantly, the limited gain bandwidth restricts them to generate ultrashort pulses approaching a few cycles or even shorter. Here we present a novel method to achieve few cycle pulses (~5 cycles) with ultra-broad spectrum (~400 nm). To our best knowledge, this is the shortest pulse width and broadest spectrum directly generated from fiber lasers. A dramatic intracavity spectral broadening can be stabilized by the unique nonlinear processes of a self-similar evolution as a nonlinear attractor in the gain fiber and a ‘perfect’ saturable absorber action of the Mamyshev oscillator. © 2018 Optical Society of America

Revealing the Underlying Mechanisms Behind TE Extraordinary THz Transmission

Suzanna Freer, Miguel Camacho, Sergei Kuznetsov, Rafael R. Boix, Miguel Beruete, and Miguel Navarro-Cia

Doc ID: 373664 Received 25 Jul 2019; Accepted 09 Nov 2019; Posted 12 Nov 2019  View: PDF

Abstract: Transmission through seemingly opaque surfaces, so-called extraordinary transmission, provides an exciting platform for strong light-matter interaction, spectroscopy, optical trapping and colour filtering. Much of the effort has been devoted to understanding and exploiting TM extraordinary transmission, while TE anomalous extraordinary transmission has been largely omitted in the literature. This is regrettable from a practical point of view since the stronger dependence of the TE anomalous extraordinary transmission on the array’s substrate provides additional design parameters for exploitation. To provide high-performance and cost-effective applications based on TE anomalous extraordinary transmission, a complete physical insight on the underlying mechanisms of the phenomenon must be first laid down. To this end, resorting to a combined methodology including quasi-optical Terahertz (THz) time-domain measurements, full-wave simulations and Method of Moments analysis, subwavelength slit arrays under s-polarized illumination are studied here, filling the void in the literature. This work reveals unequivocally the leaky-wave role of the grounded-dielectric slab mode mediating in the TE anomalous extraordinary transmission and provides the necessary frame to design practical high-performance THz components and systems.

Third Order Nonlinear Optical Susceptibility of Crystalline Oxide Yttria-Stabilized Zirconia

Guillaume Marcaud, Samuel Serna Otálvaro, Karamanis Panaghiotis, Carlos Alonso-Ramos, Xavier Le Roux, Mathias Berciano, Thomas Maroutian, Guillaume Agnus, Pascal Aubert, Arnaud Jollivet, Alicia Ruiz-Caridad, Ludovic Largeau, Nathalie Isac, Eric Cassan, Sylvia Matzen, Nicolas Dubreuil, Michel Rerat, Philippe Lecoeur, and Laurent Vivien

Doc ID: 375869 Received 30 Aug 2019; Accepted 09 Nov 2019; Posted 12 Nov 2019  View: PDF

Abstract: Nonlinear all-optical technology is an ultimate route for next generation ultra-fast signal processing of optical communication system. New nonlinear functionalities need to be implemented in photonics and complex oxides are considered as promising candidates due to their wide panel of attributes. In this context, Yttria-Stabilized Zirconia (YSZ) stands out thanks to its capability to be epitaxially grown on silicon, adapting the lattice for the crystalline oxides family of materials. We report for the first time a detailed theoretical and experimental study about the third order nonlinear susceptibility in crystalline YSZ. Via self-phase modulation induced broadening and considering the in-plane orientation of YSZ, we experimentally obtained an effective Kerr coefficient of $\widehat{n}_2^{YSZ}=4.0 \pm 2 \cdot 10^{-19} \textnormal{m}^2\textnormal{W}^{-1}$ in a 8\%mol. YSZ waveguide. In agreement with the theoretically predicted $\widehat{n}_2^{YSZ}=1.3\cdot 10^{-19} \textnormal{m}^2\textnormal{W}^{-1}$, the third order nonlinear coefficient of YSZ is comparable to the one of silicon nitride (SiN), already used in nonlinear optics. These promising results are a new step towards the implementation of functional oxides for nonlinear optical applications.

Neuromorphic Metasurface

ZHICHENG WU, Ming Zhou, Erfan Khoram, Boyuan Liu, and Zongfu Yu

Doc ID: 375886 Received 20 Aug 2019; Accepted 09 Nov 2019; Posted 12 Nov 2019  View: PDF

Abstract: Metasurfaces have been used to realize optical functions such as focusing and beam steering. They use sub-wavelength nanostructures to control the local amplitude and phase of light. Here we show that such control could also enable a new function of artificial neural inference. We demonstrate that metasurfaces can directly recognize objects by focusing light from an object to different spatial locations that correspond to the class of the object.

Non-equilibrium Hot-electron Induced Wavelength-tunable Incandescent-type Light Sources

Zhipeng Sun, Mingming Jiang, Wangqi Mao, Caixia Kan, Chongxin Shan, and De-Zhen Shen

Doc ID: 372080 Received 15 Jul 2019; Accepted 05 Nov 2019; Posted 08 Nov 2019  View: PDF

Abstract: Collective oscillation of electrons located in the conduction band of metal nanostructures being still energized electrons, with the energy up to the bulk plasmon frequency, are called non-equilibrium hot electrons. It can lead to the state-filling effect in the energy band of the neighboring semiconductor. Here, we report on the incandescent-type light source composed of Au nanorods decorated single Ga-doped ZnO microwire (ZnO:Ga MW). Benefiting from Au nanorods with controlled aspect ratio, wavelength-tunable emissions were realized, with the dominating emission peaks tuning from visible to near-infrared spectral regions. The intrinsic mechanism was found out that tunable non-equilibrium distribution of hot-electron in ZnO:Ga MW, which being injected from Au nanorods, can be responsible for the tuning emission features. In addition, upon the modification over the composition, band gap engineering, doping level, etc, the realization of electrically driven the generation and injection of non-equilibrium hot electrons from single ZnO:Ga MW with Au nanostructures coating may provide a promising platform to construct electronics and optoelectronics devices, such as electric spasers, hot-carrier induced tunneling diodes and so on.

Control of ultrafast photo-electronic dynamics of a CVD-grown graphene by ozone oxidation

Min Guo, Lai-Peng Ma, Wencai Ren, and Tianshu Lai

Doc ID: 378484 Received 24 Sep 2019; Accepted 05 Nov 2019; Posted 08 Nov 2019  View: PDF

Abstract: Diverse ultrafast dynamics have been reported on different graphene prepared by different methods. Chemical vapor deposited (CVD) growth is regarded as a most promising method for highly efficient production of graphene. However, CVD-grown graphene usually presents only one of diverse ultrafast dynamics. Thus, the control of ultrafast photo-electronic dynamics of CVD-grown graphene to present the diversity is vital for different photodetective applications of CVD-grown graphene. In this article, we report on the first realization of the control of ultrafast dynamics of CVD-grown graphene and the manifestation of diverse ultrafast dynamics on sole CVD-grown graphene. We study ultrafast photoelectronic dynamics of CVD-grown graphene with the different degree of oxidation caused by ozone oxidation using femtosecond time-resolved transient differential transmission spectroscopy, and find the ultrafast dynamics can evolve obviously with the time of ozone oxidation. The diverse ultrafast dynamics reported previously on different monolayer graphene prepared by different methods are fulfilled on sole CVD-grown graphene by controlling oxidation time. The mechanism of the manipulation of the ultrafast dynamics by ozone oxidation is revealed by Raman spectroscopy as the control of Fermi level of CVD-grown graphene. Simulations of dynamics based on optical conductivity model of graphene and Fermi level change reproduce well the observed diverse ultrafast dynamics. Our results are very important for the diverse applications of graphene and open a new path toward the diverse ultrafast dynamics on the sole graphene prepared by any method.

Strain shapes the light in photonic crystal nanocavity

Tsan-Wen Lu, Liang-Chih Wang, Cheng-Han Lai, and Po-Tsung Lee

Doc ID: 374238 Received 31 Jul 2019; Accepted 04 Nov 2019; Posted 07 Nov 2019  View: PDF

Abstract: This study proposes and demonstrates a novel nanoclamp structure symmetrically disposed nearby a one-dimensional (1D) photonic crystal (PhC) nanocavity embedded in a deformable polydimethylsiloxane substrate. These nanoclamps show capabilities of locally shaping (including enhancing and inhibiting) the strain of PhC nanocavity. The produced artificial non-ideal elastomer leads to an enhanced wavelength response of −12.7 nm for every percentage compressive strain variation from the tunable PhC nanolasers in experiments. This result not only guarantees the excellent tunability of 1D PhC nanolasers, but also promises ultrahigh sensitivity in strain sensing. Moreover, such nanoclamps can further create a reconfigurable conversion between waveguide and nanocavity with 1–2 order difference in the quality factor when applied to a 1D PhC waveguide. We believe that this study discloses a new possibility of the on-demand sculpturing optical properties of tunable PhC devices in nanoscale by inserting additional mechanical structures in nano or microscale.

Facilitated Tip-enhanced Raman Scattering by Focused Gap-Plasmon Hybridization

Houkai Chen, Yuquan Zhang, yanmeng dai, Changjun Min, Siwei Zhu, and Xiaocong Yuan

Doc ID: 378309 Received 19 Sep 2019; Accepted 04 Nov 2019; Posted 07 Nov 2019  View: PDF

Abstract: Tip-enhanced Raman Scattering (TERS) spectroscopy is a non-destructive and label-free molecular detection approach that provides high sensitivity and nanoscale spatial resolution. Therefore, it has been shown in wide applications. We demonstrate a gap-plasmon hybridization facilitated bottom-illuminated TERS configuration. The gap-plasmon hybridization effect is first performed and compared with the finite difference time domain method to optimize the parameters, and experiments are then conducted to calibrate the performance. The results demonstrate an enhancement factor of 1157 and a spatial resolution of 13.5 nm. The proposed configuration shows a great potential in related surface imaging applications in various fields of research.

Bipolar Phototransistor in Vertical Au/graphene/MoS2 Van der Waals Heterojunction with Photocurrent Enhancement

Li Jiaqi, Xurui Mao, Sheng Xie, Zhaoxin Geng, and Hongda Chen

Doc ID: 378796 Received 27 Sep 2019; Accepted 03 Nov 2019; Posted 07 Nov 2019  View: PDF

Abstract: Bipolar phototransistors have higher optical responsivity than photodiodes and play an important role in the field of photoelectric conversion. Two-dimensional materials offer a good optical responsivity and has the potential advantages of heterogeneous integration, but mass-production is difficult. In this study, a bipolar phototransistor is presented based on a vertical Au/graphene/MoS2 Van der Waals heterojunction that can be mass-produced with silicon semiconductor process using a simple photolithography process. Au is used as the emitter, which is a functional material used not just for the electrodes, MoS2 is used for the collector and graphene in used for the base of the bipolar phototransistor. In the bipolar phototransistor, the electric field of the dipole formed by the Au and graphene contact is in the same direction as the external electric field, thus enhancing the photocurrent, and a maximum photocurrent gain of 18 is demonstrated. A mechanism for enhancing the photocurrent of the graphene/MoS2 photodiode by contacting Au with graphene is also described. Additionally, the maximum responsivity is calculated to be 16458A/W and the generation speed of photocurrent is 1.48e-4A/s.

808 nm Laser Triggered Self-monitored Photo-thermal Therapeutic Nanosystem Y2O3: Nd3+/Yb3+/Er3+@SiO2@Cu2S

Chongfeng Guo, Zhiyu Zhang, Hao Suo, and Xiaoqi Zhao

Doc ID: 376327 Received 04 Sep 2019; Accepted 28 Oct 2019; Posted 01 Nov 2019  View: PDF

Abstract: A multifunctional photo-thermal therapeutic nano-platform Y2O3: Nd3+/Yb3+/Er3+@SiO2@Cu2S (YR-Si-Cu2S) was designed through a core-shell structure, expressing the function of bio-tissue imaging, real-time temperature detection and photo-thermal therapy under 808 nm. In this system, the core Y2O3: Nd3+/Yb3+/Er3+ (YR) takes the responsibility of emitting optical information and monitoring temperature, while the shell Cu2S nano-particles carry the most of photo-thermal conversion function. The temperature sensing characteristic was achieved by the fluorescence intensity ratio (FIR) technique using the thermal coupling energy levels 4S3/2/2H11/2 of Er3+, and their higher accuracy for real-time temperature measurement in the bio-tissue than that of infrared thermal imager was also proved by sub-tissue experiments. Furthermore, the photo-thermal effect of the present nano-system Y2O3: Nd3+/Yb3+/Er3+@SiO2@Cu2S was confirmed by Escherichia colibacteria (E. coli) and Staphylococcus aureus (S. aureus) ablation. Results indicate that YR-Si-Cu2S has application prospect in temperature-controlled photo-thermal treatment and imaging in bio-tissues.

Lithium niobate waveguides with high-index contrast and preserved nonlinearity fabricated by High Vacuum Vapor-phase Proton Exchange

Alicia Rambu, Alin Apetrei, Florent Doutre, Hervé Tronche, Vasile Tiron, Marc Micheli, and Sorin Tascu

Doc ID: 373424 Received 29 Jul 2019; Accepted 24 Oct 2019; Posted 25 Oct 2019  View: PDF

Abstract: Highly confining waveguides (∆ne>0.1) without degraded nonlinear coefficient and low propagation losses have been fabricated in lithium niobate by a new process that we called High Vacuum Vapor-phase Proton Exchange (HiVac-VPE). Index contrast, index profile, nonlinearity and crystallographic phases are carefully investigated. Original analysis of index profiles indicates that the waveguides contains sub-layers whose depths are depending on the exchange durations. Propagation behavior, propagation losses and Second Harmonic Generation (SHG) response of HiVac-VPE channel waveguides are investigated at telecom wavelength. The results recommend HiVac-VPE as very promising technique for fabricating efficient nonlinear photonic integrated circuits in LN crystals.

Experimental demonstration of full-field quantum optical coherence tomography

Roberto Ramirez Alarcón, Zeferino Ibarra, Carlos Sevilla Gutiérrez, HECTOR CRUZ-RAMIREZ, and Alfred U'Ren

Doc ID: 375318 Received 14 Aug 2019; Accepted 05 Oct 2019; Posted 08 Oct 2019  View: PDF

Abstract: We present to the best of our knowledge the first implementation of full-field quantum optical coherence tomography (FF-QOCT). In our system, we are able to obtain full 3D information about the internal structure of a sample under study by relying on transversely-resolved Hong Ou Mandel (HOM) interferometry with the help of an intensified CCD (ICCD) camera. Our system requires a single axial scan, obtaining the full-field transverse single-photon intensity in coincidence with the detection of the sibling photon, for each value of the signal-idler temporal delay. We believe that this capability constitutes a significant step forward towards the implementation of QOCT as a practical biomedical imaging technique.

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