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Accepted papers to appear in an upcoming issue

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Direct and cascaded collective third-harmonic generation in metasurfaces

Ofer Doron, Lior Michaeli, and Tal Ellenbogen

Doc ID: 359927 Received 11 Feb 2019; Accepted 21 May 2019; Posted 21 May 2019  View: PDF

Abstract: We use collective interactions in plasmonic metasurfaces to manipulate the interplay between direct and cascaded third-harmonic generation. We implement a simple case where in contrast to the direct contribution, which is mainly enhanced by the local plasmonic resonances, the cascaded contribution enhancement may be manipulated using the metasurface's geometry, in addition to the single nanoparticle's electrical response, by enabling the proper-nonlocal interactions at the second-harmonic frequency. In addition, an anomalous phase relation of the single nanoparticle's linear polarizability at the second-harmonic region affects the relative phase between the direct and cascaded contributions which results in a Fano-like asymmetrical line shape of the third-harmonic generation. We demonstrate that this can be used to enhance or contrarily completely eliminate the third-harmonic generation from metasurfaces over a very narrow bandwidth.

On the VO2 Metasurface-Based Temperature Sensor

Muhammad Baqir and Pankaj Choudhury

Doc ID: 361430 Received 04 Mar 2019; Accepted 21 May 2019; Posted 22 May 2019  View: PDF

Abstract: A specially designed vanadium oxide (VO2) metasurface-based temperature sensor was investigated. In the configuration, stacked silicon dioxide (SiO2) and aluminum oxide (Al2O3) multilayered structure was used, wherein the top metasurface has sub-wavelength-sized periodically arranged VO2 nano-discs (in the form of array), and the bottom silver (Ag) layer acts as a perfect reflector. Spectral characteristics and sensitivity of the structure were observed under varying temperature. Apart from these, the effects of nano-disc radius, thickness of top metasurface and incidence angle (of light impinging the metasurface) on the spectral features were also reported.

Photonic crystal nanobeam cavities with optical resonances around 800 nm

Ivens Saber, Rajiv Boddeda, Fabrice Raineri, Dorian Sanchez, Grégoire Beaudoin, Isabelle Sagnes, Quentin Glorieux, Alberto Bramati, J. Ariel Levenson, and Kamel Bencheikh

Doc ID: 361987 Received 26 Mar 2019; Accepted 21 May 2019; Posted 22 May 2019  View: PDF

Abstract: We report on the design and the fabrication of 1D photonic crystal (PhC) nanobeam cavities with optical resonances around 800\,nm, compatible with Rubidium, Cesium or Argon atomic transitions. The cavities are made of Indium Gallium Phosphide (InGaP) material, a III-V semi-conductor compound which has a large index of refraction ($n \simeq 3.3$) favoring strong optical confinement and small mode volumes. Nanobeam cavities with inline and side coupling have been designed and fabricated, and quality factors up to $2\times 10^4$ have been measured.

Optical Properties of a few Semiconducting Hetero-structures in the Presence of Rashba Spin-Orbit Interactions: a two-Dimensional Finite Difference Numerical Approach

Maryam Sabzevar, Mohammah Ehsani, mehdi solaimani, and GHORBANI MEHRZAD

Doc ID: 365033 Received 15 Apr 2019; Accepted 19 May 2019; Posted 20 May 2019  View: PDF

Abstract: In the present study, the effect of Rashba spin-orbit interactions on the electron energy states, spin density distributions and absorption coefficient of a few two-dimensional quantum dots with different confining potentials have been studied. We have used a finite difference method to solve the resulting coupled Schrodinger equations. In our computations, since the concluded Hamiltonian matrix was found to be extensive; regardless of being blocked and sparse, it was required to implement the Arnoldi factorization method for diagnolizing the Hamiltonian matrix. According to results, it was found that the interstate mixing stemmed from the Rashba spin-orbit interaction can result in a new spin polarization. This occurrence explicitly justifies the observation of multiple peaks in the spin density distributions. Furthermore, by increasing the quantum dot size, the absorption coefficient increases about four times. Finally, with the increasing of the Rashba parameter, the absorption peak decreases and a redshift takes place.

Reconstruction of laser envelopes by infrared field dressed single photoionization

Feng Wang, Kai Liu, Meiyan Qin, Qing Liao, Pengfei Lan, and Peixiang Lu

Doc ID: 360730 Received 21 Feb 2019; Accepted 19 May 2019; Posted 20 May 2019  View: PDF

Abstract: Attosecond pump-probe experiments are conceived as a powerful tool to investigate the ultrafast electron dynamics. In order to accurately probe the electron motion, the ultraviolet (UV) and infrared (IR) fields should be carefully characterized. Here, we theoretically propose a method for reconstruction of laser envelopes by IR field dressed single-photon UV ionization of hydrogen. By simulating the photoelectron spectrum for different time delays between the IR and UV fields, we show that the envelope of UV field can be retrieved from the central peak of photoelectron spectrum when the IR and UV fields separate completely in time. With the retrieved envelope of UV field, the envelope of IR field can be further characterized by the delay-dependent intensity ratio between sideband and central peaks. Our method is robust for reconstructing the envelope of more complex laser fields.

Interference of nonpolarized light in liquid crystal domains on the polymer surface

Alexander Parshin, Alexey Barannik, Vasiliy Shabanov, and Victor Zyryanov

Doc ID: 361599 Received 04 Mar 2019; Accepted 18 May 2019; Posted 20 May 2019  View: PDF

Abstract: The interference of the nonpolarized light transmitted through an ensemble of nematic liquid crystal domains formed on the polycarbonate surface has been investigated. A model based on the superposition of the ordinary and extraordinary beams passed through domains with the radial structure has been proposed. Expressions for the phase difference and intensity of the interfering beams, which take into account the distribution of the liquid crystal director field, have been derived. The dependences of the optical transmittance of a domain layer on the applied voltage have been calculated with regard to the material and optical constants of a liquid crystal and structural features and averaged morphological parameters of individual domains in the experimental sample. The results of the calculation are consistent with the experimental data, which confirms the validity of the proposed model.

Thomson backscattering in combined uniform magnetic and envelope modulating circularly-polarized laser fields

B.S. Xie and Julia Zhu

Doc ID: 360032 Received 12 Feb 2019; Accepted 18 May 2019; Posted 20 May 2019  View: PDF

Abstract: The Thomson backscattering spectra in combined uniform magnetic and cosine-envelope circularly-polarized laser fields are studied in detail. With an introduction of the envelope modulation, the radiation spectra exhibit high complexity attributed to the strong nonlinear interactions. On the other hand, four fundamental laws related to the scale invariance of the radiation spectra are analytically revealed and numerically validated. They are the laws for the radiation energy as the $6$th power of the motion constant exactly, also as the approximate negative $6$th power with respect to the initial axial momentum and laser intensity in a certain of conditions, respectively, and finally an important self-similar law, i.e., when the circular laser frequency, the envelope modulation frequency, and the modified cyclotron frequency are simultaneously increased by a factor, the radiation energy will be increased by the second power of that factor without changing the shape of the spectrum. With the application of these laws, especially the last one, a much higher radiation energy can be obtained and the harmonic at which the maximum radiation occurs can be precisely tuned without changing its amplitude. These findings provide a possible way to advance radiation technology in many fields such as medicine, communications, astrophysics, and security.

Design and analysis of Long-Period Fiber Gratings in tapered multimode chalcogenide glass fiber for temperature measurement

Leilei Wang, wenqiang ma, Peiqing Zhang, Dan Yang, Liang Zhu, Xunsi Wang, and Shixun Dai

Doc ID: 364004 Received 04 Apr 2019; Accepted 18 May 2019; Posted 20 May 2019  View: PDF

Abstract: A high sensitive temperature sensor based on long-period fiber gratings (LPFGs) in tapered multimode chalcogenide fiber was designed. The transmission characteristics of this LPFGs and their temperature sensitivities of different cladding modes with variations in the waist diameters and surrounding refractive indices (SRIs) were theoretically studied. Simulation results showed that the temperature sensitivities of LPFGs could be effectively increased by reducing the waist diameter. The temperature sensitivity of the proposed LPFGs with a 75 µm waist diameter at the lowest LP₀₂ cladding mode was calculated to be 1.89 nm/°C at 1.55 µm. When the grating period of the designed LPFG is selected at its dispersion-turning-point, the temperature sensitivity can achieve a maximum absolute value of 15.2 nm/°C at 1.55 μm, which is approximately 160 times higher than that of conventional silica LPFGs. The influences of variations in SRIs on resonant wavelength and temperature sensitivity of this LPFGs were very weak due to the relatively large cladding refractive index, which indicated that this sensor showed a high stability against changes in SRIs. Therefore, this designed sensor can be used in complex environments where high precision temperature measurements are required.

On the control of the momentum distribution of paired photons generated by non-collinear type-II spontaneous parametric down-conversion

OMAR CALDERÓN and Alejandra Valencia

Doc ID: 358841 Received 30 Jan 2019; Accepted 16 May 2019; Posted 16 May 2019  View: PDF

Abstract: We present a theoretical and experimental characterization of the joint spatial distribution of paired photons generated via non-collinear type-II SPDC. Specifically, for the photons created parallel and perpendicular to the optical table, we determine the shape of such distributions and the degree of correlation of these photons. The characterization is done for different sizes of the pump beam waist. We found that it is possible to have different spatial distributions of the photons with the same degree of correlation.

Electromagnetically induced transparency of a single frequency comb mode

Ivor Kresic, Mateo Kruljac, Ticijana Ban, and Damir Aumiler

Doc ID: 361122 Received 26 Feb 2019; Accepted 16 May 2019; Posted 16 May 2019  View: PDF

Abstract: We measure the electromagnetically induced transparency of a single frequency comb mode interacting with laser cooled $^{87}$Rb atoms.A~$\Lambda$ hyperfine level structure in a D2 transition is used in the configuration of co-propagated probe (frequency comb) and coupling (continuous-wave) laser fields.The signature of EIT in the transmission of a single comb mode as well as the radiation pressure force is experimentally detected.The results are satisfactorily reproduced by the developed theoretical models, where EIT is seen to occur due to coherent accumulation. Our results could find application in quantum computing and communication with optical frequency combs.

Absorption leads to narrower plasmonic resonances

Ryan Peck, Alexandre Brolo, and Reuven Gordon

Doc ID: 362441 Received 14 Mar 2019; Accepted 16 May 2019; Posted 16 May 2019  View: PDF

Abstract: While it is generally accepted that adding loss dampens and broadens plasmonic resonances, here we find adding losses can actually narrow the linewidth and increase the resonance peak. We show that the scattering cross section of a metal nanoparticle in a lossy dielectric medium is an order of magnitude larger than the same nanoparticle in a lossless dielectric. The full width at half maximum is a quarter of that of the non-absorbing medium. The peak narrowing and increased scattering has benefits for biomarkers where high scattering efficiency and narrow linewidths (for denser multiplexing) is desired. The enhanced scattering and absorption in the surrounding lossy medium is also beneficial for photovoltaic applications.

Absolute frequency measurement of molecular iodinehyperfine transition at 534 nm

Ke Deng, Feihu Cheng, Kui Liu, Hongli liu, Jie Zhang, and Zehuang Lu

Doc ID: 352801 Received 06 Dec 2018; Accepted 16 May 2019; Posted 21 May 2019  View: PDF

Abstract: We report absolute frequency measurements of 21 hyperfine components of the rovibrational transition of molecular iodine R(53) 31-0 transitions at 534 nm with an optical frequency comb. The 534 nm laser, which is frequency-doubled from a 1068 nm external-cavity diode laser, is frequency stabilized to a hyperfine component of the ¹²⁷I₂ R(53) 31-0 transition using the modulation transfer spectroscopy. A frequency stability of 7× 10-¹² at 1 s averaging time is achieved when its frequency is stabilized to the a₂₁ component. To obtain the absolute frequency, the pressure shift and power shift of the a₂₁ component are investigated. The observed hyperfine transitions of the iodine can be good frequency references at 534 nm and are especially useful for research on the aluminum ion because the frequency of the iodine hyperfine transitions are close to the second sub-harmonic frequency of the ¹S₀ - ³P₁ transition of aluminum ionat 267 nm.

Interplay between Raman self-frequency shift and cross-phase modulation in vector-soliton of a birefringent fiber

Shailendra Varshney and Vishwatosh Mishra

Doc ID: 362563 Received 18 Mar 2019; Accepted 15 May 2019; Posted 20 May 2019  View: PDF

Abstract: The competition between the cross-phase modulation (XPM) and the Raman induced red frequency shift is observed in the orthogonally polarized components (in form of optical pulses) of a vector-soliton propagating in the fundamental mode of a birefringent fiber exhibiting negative third-order dispersion and group velocity birefringence. Both pulses experience opposite frequency shifts due to XPM which reinforces the Raman self-frequency shift of one pulse while it hinders the self-frequency shift of the other. A large red-shift in one of the pulses of vector-soliton suggests transfer of greaterpart of its energy to the dispersive radiation, leading to an asymmetry in the longitudinal evolution of the amplitudes as well as the frequencies of both the pulses of the vector-soliton. To support our analysis, an analytical approach is developed in order to understand the interplay between Raman effect and the XPM. The findings of the analytical approach are in good qualitative agreement with the numerical results, which is consistent with the results of [Phys. Rev. E 70, 016615 (2004)]. The derived analytical relations accommodate additional nonlinear interactions originating from the XPM as well as mutual Raman interaction which makes our approach much superior than used in [Phys. Rev. E 70, 016615 (2004)]. It is also possible to understand the interaction between two frequency-shifted solitons in a true single-mode fiber or other waveguide systems exhibiting negative third-order dispersion by a slight modification of our theoretical approach.

Polarization switching between parallel and orthogonal collective resonances in arrays of metal nanoparticles

Alina Muravitskaya, Artur Movsesyan, Sergei Kostcheev, and Pierre-Michel Adam

Doc ID: 359305 Received 31 Jan 2019; Accepted 13 May 2019; Posted 14 May 2019  View: PDF

Abstract: In this work we discuss the excitation of orthogonal and parallel collective resonances in rectangular arrays of aluminum nanoparticles and switch between them with a change of the array dimensions or polarization. We study the difference of the far-field interactions in the array for both homogeneous and heterogeneous refractive index environment and their influence on the nature of the coupling. We also explain the origin of the parallel coupling which was unclear previously. The rate of the parallel coupling depends on the interparticle distance which allows us to control the intensity of the coupled mode.

Optical bistability of graphene embedded in parity-time-symmetric photonic lattices

Dong Zhao, Shaolin Ke, Hu Yonghong, Bing Wang, and Peixiang Lu

Doc ID: 361148 Received 04 Mar 2019; Accepted 13 May 2019; Posted 14 May 2019  View: PDF

Abstract: We investigate the optical bistability of graphene in parity-time-symmetric (PT-symmetric) photonic lattices incorporated with a defect. The field localization of the defect mode can strengthen the nonlinearity of graphene to achieve low-threshold bistability. The nonlinearity is further enhanced and the bistability threshold decreases by increasing the gain-loss factor in the PT-symmetric structure. The interval of upper and lower bistability thresholds is broadened as the exceptional points split. Moreover, we show the phase transition from bistability to non-bistability by modulating the incident wavelength and chemical potential of graphene. The study may find great applications in all-optical switches and optical storage.

Sub-picosecond flat-top pulse shaping using a hybrid plasmonic microring-based temporal differentiator

Azadeh Karimi, Abbas Zarifkar, and Mehdi Miri

Doc ID: 361547 Received 04 Mar 2019; Accepted 10 May 2019; Posted 13 May 2019  View: PDF

Abstract: Design of a fractional-order photonic temporal differentiator, based on the silicon hybrid plasmonic add-drop microring resonators is proposed. Because of the strong light confinement in the hybrid plasmonic waveguides, the overall footprint of the differentiator is significantly reduced. The numerical simulation results show that the differentiator can reach considerably wide 3dB bandwidth of about 2.5 THz (20 nm) with the microring radius of 1.2 m. It is also shown that the differentiation order and the 3dB bandwidth of the proposed structure can be tuned in the range of [0.6 1.0] and [1.74 2.5] THz ([14 20] nm), respectively, by modifying the geometrical parameters of the differentiator. Mentioned bandwidth is higher than the previously reported values for microring based photonic differentiators. Furthermore, the wide bandwidth and the tunable differentiation order of the structure along with its compact footprint makes it a promising choice for the processing of ultrashort optical pulses. Generation of short flat-top pulses from input Gaussian pulses is then considered as an example of such applications. It is shown through three-dimensional finite-difference time-domain (3D FDTD) simulations that the proposed differentiator can be used to generate a flat-top pulse with the flat duration of 330 fs and the FWHM of ~1 ps, from an ultrashort Gaussian input pulse, with the FWHM of 490 fs.

Optical response of rectangular array of elliptical plasmonic particles on glass revealed by Mueller matrix ellipsometry and Finite Element Modelling

Per Magnus Walmsness, Thomas Brakstad, Brage Svendsen, Jean-Phillipe Banon, John Walmsley, and Morten Kildemo

Doc ID: 359370 Received 05 Feb 2019; Accepted 09 May 2019; Posted 13 May 2019  View: PDF

Abstract: We report here on the optical response of strongly anisometric gold particles arranged in a rectangular lattice on glass when probed at non-normal incidence in reflection using spectroscopic Mueller matrix ellipsometry in the energy range 0.73-5.9 eV. The localized surface plasmon resonances, reshaped through Rayleigh anomalies, are mapped out by full azimuthal rotation of the sample. The experimental Mueller matrices are discussed and interpretation is supported by finite element modelling of the Mueller-Jones matrix elements. The data show a strong anisotropic optical response of the localized surface plasmon resonances as a function of the azimuthal angle of incidence, and Rayleigh-Wood anomalies are clearly observed in the data. We also observe a mixing of the Rayleigh modes and the localized surface plasmon resonances with an associated strong polarization coupling. We further argue the importance of Mueller matrix ellipsometry for metrology in the manufacture of metasurfaces, for understanding the effect of the lattice in metasurface design, and finally in validating computational methods.

Impact of various mechanisms of photorefractive effect on polarization singularities generation during the self-focusing of Gaussian beam in isotropic medium

Kirill Grigoriev and Vladimir Makarov

Doc ID: 362302 Received 12 Mar 2019; Accepted 09 May 2019; Posted 09 May 2019  View: PDF

Abstract: The emerging of polarization singularity lines (C-lines), accompanying the self-focusing of initially elliptically polarized Gaussian beam in isotropic medium with various mechanisms of cubic nonlinearity is studied numerically. Lines of circular polarization can appear in planes perpendicular to the beam axis as circles centered at the axis in both sub-threshold and super-threshold regimes of nonlinear self-action. The range of beam power values, for which the C-lines are formed, is rapidly expanding as the initial polarization of the beam gets closer to circular. The radius of the first formed C-line and the distance from the C-line to the border of the medium are decreasing if the beam power gets bigger.

Polarization-selective defect mode amplification in a photonic crystal with intracavity 2D arrays of metallic nanoparticles

Sergey Moiseev, Igor Glukhov, Yuliya Dadoenkova, and Florian F.L. Bentivegna

Doc ID: 362328 Received 14 Mar 2019; Accepted 07 May 2019; Posted 09 May 2019  View: PDF

Abstract: We demonstrate the possibility of polarization-selective amplification of a defect mode in an active multilayered photonic crystal through the resonant excitation of surface plasmons in a 2D ordered array of metallic nanoparticles embedded in the structure. Such an array acts as a polarizer whose spectral characteristics are defined by the shape of the nanoparticles and the periodicity of the array. The modal selectivity of the photonic structure is due to the strong surface plasmon assisted scattering of light by anisotropic nanoparticles which depends on the relative orientations of their anisotropy axis and the polarization direction of the incoming light wave. The spectral and polarimetric characteristics of the photonic structure are calculated using the transfer matrix formalism. The 2D array of nanoparticles is described within the coupled-dipole approximation and is associated with a matrix whose elements depend on the geometry of the array and the polarization of the radiation. We show that in order to achieve defect mode amplification for a chosen polarization in such a heterostructure, the position of the array of nanoparticles should be made to coincide with regions of high optical field localization. We also determine the structural characteristics of the nanoparticle array that enhance the sensitivity of the spectral behavior of the photonic heterostructure to the polarization state of the incoming light beam.

Creation of a unequal-weighted four-mode square cluster state in a ring cavity

Gaoxiang Li, Yan Yan, Ge Huang, and Zhi-dong Zhou

Doc ID: 360380 Received 19 Feb 2019; Accepted 07 May 2019; Posted 07 May 2019  View: PDF

Abstract: Four-mode continuous-variable (CV) cluster states are an important and necessary resource in continuous variable quantum computation. In this paper, we present a simple and efficient scheme to realize a unequal-weighted four-mode square CV cluster state using atomic ensembles driven by seven strong classical laser fields. It just needs a single selection about the appropriate squeezing parameters and pump laser parameters. With the unique squeezing operator and a new unitary transformation, we show that seven laser fields drive four atomic ensembles into a stationary four-mode squeezed vacuum state via the cavity dissipation.

Design of high efficiency-small size passive all-optical diodes based on photonic crystal and graphene

mohammad malekmohammad, Mozhde Janfada, and Mahmood Soltanolkotabi

Doc ID: 362649 Received 18 Mar 2019; Accepted 07 May 2019; Posted 14 May 2019  View: PDF

Abstract: Light propagation in an asymmetric multilayered structure, composed of a linear defective photonic crystal and nonlinear graphene layer, is theoretically investigated. (BA)^4/Graphene/(AB)^4 (AABB)^4 structure with a slight perturbation in (AABB)^4 part can provide non-reciprocal transmission to achieve an optical diode. This structure was optimized in order to have low operation input intensity, high contrast, small size all-optical diode without an additional pump signal. In this work, four passive all-optical diodes are presented. The best contrast ratio is 6.3 and the minimum operation input intensity for diode action is 2.7×〖10〗^(-3) MW/〖cm〗^2 . This structure gives an all-optical diode having smaller size and higher efficiency in comparison to previous works.

Analytic theory for lasers based on stimulated polariton scattering

David Spence, Helen Pask, and Andrew Lee

Doc ID: 362331 Received 12 Mar 2019; Accepted 06 May 2019; Posted 06 May 2019  View: PDF

Abstract: We present a model for predicting the development of Stokes and THz fields undergoing stimulated polariton scattering. The model is valid for finite beams, avoiding the most limiting assumption of the leading model to date; our model makes significantly different predictions for narrow pump beams and low-gain systems now commonly being studied. The model accounts for the build-up of the THz field across finite pump beams, as well as naturally extending that propagation away from the pumped region, a key requirement for understanding the effectiveness of real experimental geometries.

Beam combining scheme of high-power broad-area semiconductor lasers with Lyot-filtered reinjection: modeling, simulations, and experiments

Carsten Bree, Volker Raab, JOAN PONSODA, Guillermo Werner, Kestutis Staliunas, Uwe Bandelow, and Mindaugas Radziunas

Doc ID: 364403 Received 08 Apr 2019; Accepted 05 May 2019; Posted 07 May 2019  View: PDF

Abstract: A brightness- and power-scalable polarization beam combining scheme for high-power, broad-area semiconductor laser diodes is investigated numerically and experimentally. To achieve the beam combining, we employLyot-filtered optical reinjection from an external cavity, which forces lasing of the individual diodes on interleaved frequency combs with overlapping envelopes and enables a high optical coupling efficiency. Unlike conventional spectral beam combining schemes with diffraction gratings, the optical coupling efficiency is insensitive to thermal drifts of laser wavelengths. This scheme can be used for efficient coupling of a large number of laser diodes and paves the way towards using broad-area laser diode arrays for cost-efficient material processing, which requires high-brilliance emission and optical powers in the kW-regime.

Propagation of terahertz surface plasmon polaritons around a convex metal-dielectric interface

Boris Knyazev, Vasily Gerasimov, Aleksey Nikitin, Ivan Azarov, and Yulia Choporova

Doc ID: 361450 Received 08 Mar 2019; Accepted 05 May 2019; Posted 06 May 2019  View: PDF

Abstract: The results of experimental studies of the attenuation of surface plasmon polaritons (SPPs) in the terahertz range excited by free-electron laser radiation (λ = 129 and 141 μm) on the gold-ZnS-air cylindrical interfaces are presented in this paper. Because of the additional radiation losses, associated with the curvature of the surface, the attenuation of SPPs in this case significantly exceeds the attenuation of SPPs propagating on a flat surface of the metal. An optoacoustic cell and a microbolometer matrix measured the intensity of plasmons propagating around cylinders of radii of 60 and 30 mm as a function of the azimuthal angle via recording the bulk waves emitted tangentially from the plasmon track. The radiation losses increase with decreasing radius of curvature. In the case of a cylinder with a radius of 60~mm, an increase in the thickness of the dielectric film first reduced the losses to the minimum value at a layer thickness of 1.5 μm, and then the losses sharply grew up.

Blue-Red Color Tunable All-Inorganic Bromide-Iodide Mixed Halide Perovskites for White Light-Emitting Diodes

Saroj Thapa, Gopi Adhikari, Hongyang Zhu, and Peifen Zhu

Doc ID: 351639 Received 12 Nov 2018; Accepted 04 May 2019; Posted 06 May 2019  View: PDF

Abstract: Here, we presented the synthesis of all-inorganic mixed halide CsPb(Br1-xIx)3 perovskites at an ambient atmosphere with color-tunable emission (464-667 nm) having narrow emission line-width ( -47 nm) by employing a newly reported saponification process in our laboratory. This inert gas-glovebox free protocol synthesis technique offers a simplicity and low-cost in the preparation of high-quality nanocrystals. Notably, nanocrystals with different emission wavelength resulted in tunable correlated-color temperature (2513-9783 K) while maintaining a high color-rendering index (up to 95), desirable for white light. Thus, the experimental results suggest that the saponification processed nanocrystals obtained in this work can be used for future indoor-illuminations.

The photon - the role of its mode function in analyzing complementarity

Axel Heuer, Ralf Menzel, Robert Elsner, Dirk Puhlmann, and Wolfgang Peter Schleich

Doc ID: 355666 Received 18 Dec 2018; Accepted 03 May 2019; Posted 06 May 2019  View: PDF

Abstract: We investigate the role of the mode function in a single photon experiment demonstrating the complementarity principle while varying the "which path"-information. Using entangled photons created by spontaneous parametric down-conversion from a pump mode in a TEM_01-mode in a double-slit experiment allows new insights. Indeed, when the signal photons interfering at the double-slit belong to this double-hump mode we obtain almost perfect visibility of the interference fringes and no "which-slit" information is available. This result is remarkable because the entangled signal and idler photon pairs are created each time in one of the two intensity humps, only [16]. However, when we break the symmetry between the two maxima of the mode structure by mixing in components of other modes via the reference detection of the entangled idler photons, the paths through the slits for these additional photons become distinguishable and the visibility vanishes. It is the mode function of the photons selected by the detection system which decides if interference, or "which-slit" information is accessible in the experiment.

Generation of mid-infrared and visible radiation in a multi-band phase-matched sub-wavelength LiNbO₃ waveguide

Brett Carnio and Abdulhakem Elezzabi

Doc ID: 356633 Received 16 Jan 2019; Accepted 03 May 2019; Posted 06 May 2019  View: PDF

Abstract: An on-chip lithium niobate (LiNbO3) waveguide platform is proposed that simultaneously produces electric field pulses through sum and difference frequency generation. By controlling the geometry of the waveguide, perfect phase-matching is achieved across multiple spectral bands, spanning from visible to mid-infrared. The waveguide confines the sum frequency generation wavelengths to the waveguide core and allows the difference frequency generation wavelengths to be emitted as Cherenkov waves. A finite-difference time-domain analysis is performed to study this multi-band generation, where the LiNbO3 waveguide produces electric field pulses at a conversion efficiency of 14×10-5 and 0.5×10-5 through sum and difference frequency generation, respectively. This waveguide platform provides suitable design flexibility, since the emission wavelengths are adjustable through proper choice of the waveguide core width and the excitation wavelengths. This source allows for better utilization of on-chip space by reducing the total number of devices necessary to achieve multi-band light generation.

Exceptional points for resonant states on parallel circular dielectric cylinders

Amgad Abdrabou and Ya Yan Lu

Doc ID: 362147 Received 11 Mar 2019; Accepted 03 May 2019; Posted 06 May 2019  View: PDF

Abstract: Exceptional points (EPs) are special parameter values of a non-Hermitian eigenvalue problem where eigenfunctions corresponding to a multiple eigenvalue coalesce. In optics, EPs are associated with a number of counter-intuitive wave phenomena, and have potential applications in lasing, sensing, mode conversion and spontaneous emission processes. For open photonic structures, resonant states are complex-frequency solutions of the Maxwell's equations with outgoing radiation conditions. For open dielectric structures without material gain or loss, the eigenvalue problem for resonant states can have EPs, since it is non-Hermitian due to radiation losses. Motivated by potential applications in nanophotonics, we study EPs of resonant states for finite sets of parallel infinitely-long circular dielectric cylinders with subwavelength radii. For systems with two, three and four cylinders, we present examples for second and third order EPs and highlight their topological features. Our work provides insight to understanding EPs on more complicated photonic structures, and can be used as a simple platform to explore applications of EPs.

High-efficiency transverse-fields-acceleration by laser with spatially variant state-of-polarization.

Hai Lin and Chengpu Liu

Doc ID: 356651 Received 07 Jan 2019; Accepted 03 May 2019; Posted 03 May 2019  View: PDF

Abstract: Strict single-body dynamics theory and numerical experiment on particle acceleration by the laser with a class of spatially variant state-of-polarization is presented. Because such a class of spatially variant state-of-polarization also corresponds to a spatially variant, over wavelength-level space scale, intensity profile, it can cause electronic response to the driving field to be dependent on its initial transverse position. Suitable value of the initial transverse position can correspond to a suitable phase delay between electronic transverse oscillating velocity $\upsilon$ and the driving electric field $E$, which leads to $-e\int_{0}^{t} E\cdot \upsilon dt^{'}>0$, and hence implies aperiodic time growth rate of electronic kinetic energy. Under a same value of laser power, electronic energy gain can be several orders of magnitude higher than that in the case of a spatially homogeneous state-of-polarization. This suggests that choosing suitable state-of-polarization is an efficient way of achieving compact high-efficient accelerator.

Particle-modified polymeric cladding on glass optical fibers enhances radial light scattering

Mariana Lanzarini-Lopes, Sergi Garcia-Segura, Kiril Hristovski, Mike Messerly, A.J. Simon, and Paul Westerhoff

Doc ID: 359937 Received 19 Feb 2019; Accepted 01 May 2019; Posted 02 May 2019  View: PDF

Abstract: Radially light-emitting optical fibers are of increasing interest for applications in medicine, visible aesthetics, and environmental remediation. Optical fibers contain a light guiding core coated by protective polymer layers (cladding and coating), which assure both the strength and flexibility of the optical fiber. This paper examines the feasibility of scattering light radially from fibers by loading the fiber cladding with particle scattering centers during the optical fiber fabrication process. This work uses an in-line full-scale scalable facility to coat the fibers and control the polymer cladding and silica sphere. Loadings up to 2.0 % wt. of 500-nm silica particles on the cladding of the optical fiber led to an average of 80 times higher scattering for visible light and up to 30 times higher in the UVA wavelength range compared against cladding without particle modifications. This study illustrated feasibility of fabricating broad-band light scattering optical fibers for use with modified polymeric cladding.

Core Size and Axial Offset Dependent Extinction Characteristics for Silver Nanotube and its Application to Directional Sensing

Alexander Iskandar, Suhandoko Isro, and May-On Tjia

Doc ID: 362572 Received 15 Mar 2019; Accepted 01 May 2019; Posted 02 May 2019  View: PDF

Abstract: We report the results of study using the classical Mie theory and available experimental data on the extinction spectra resulted from TE polarized wave incident upon a silver nanotube with dielectric core. It is shown that the spectral changes separately induced by varied core radius ($R_{in}$) and the axial offset ($d$) are consistent with those reported for gold spherical nanoshell calculated by the celebrated plasmon hybridization (PH) model, including the core offset induced symmetry breaking effect. This is followed by an analysis of the combined influences of $R_{in}$ and $d$ on the extinction efficiency $Q_{ext}$, which results in the optimal geometrical parameters of $R_{in} = 31.5$ nm, $d = 16$ nm and Ag minimum shell thickness $\Delta = 2.5$ nm for the maximum $Q_{ext}$ at the resonance wavelength of $\lambda = 756$ nm. The different axial offsets are further shown to exhibit interesting variations of the angular distribution of the corresponding scattered wave intensity, which reveals significantly sensitive variations to different incident wave directions. The result has thus led to the following study for the exploration and demonstration of its potential development for sensing the direction of incoming TE polarized waves.

Nonlinear optics of photonic hyper-crystals: optical limiting and hyper-computing

Igor Smolyaninov

Doc ID: 358376 Received 23 Jan 2019; Accepted 30 Apr 2019; Posted 02 May 2019  View: PDF

Abstract: Photonic hyper-crystals combine the most interesting features of hyperbolic metamaterials and photonic crystals. Since the dispersion law of extraordinary photons in hyperbolic metamaterials does not exhibit the usual diffraction limit, photonic hyper-crystals exhibit light localization on deep subwavelength scales, leading to considerable enhancement of nonlinear photon-photon interaction. Therefore, similar to their conventional photonic crystal counterparts, nonlinear photonic hyper-crystals appear to be very promising in optical limiting and optical computing applications. Nonlinear optics of photonic hyper-crystals may be formulated in such a way that one of the spatial coordinates would play a role of effective time in a 2+1 dimensional “optical spacetime” describing light propagation in the hyper-crystal. Mapping the conventional optical computing onto nonlinear optics of photonic hyper-crystals results in a “hyper-computing” scheme, which may considerably accelerate computation time.

Coupling phenomena and collective effects in resonant meta-atoms supporting both plasmonic and (opto-)magnetic functionalities: an overview of properties and applications

Nicolò Maccaferri

Doc ID: 359244 Received 31 Jan 2019; Accepted 29 Apr 2019; Posted 29 Apr 2019  View: PDF

Abstract: We review both the fundamental aspects and the applications of functional magneto-optic and opto-magnetic metamaterials displaying collective and coupling effects on the nanoscale, where the concepts of optics and magnetism merge to produce unconventional phenomena. The use of magnetic materials instead of the usual noble metals allows for an additional degree of freedom for the control of electromagnetic field properties, as well as it allows light to interact with the spins of the electrons and to actively manipulate the magnetic properties of such nanomaterials. In this context, we explore the concepts of near-field coupling of plasmon modes in magnetic meta-molecules, as well as the effect of excitation of surface lattice resonances in magneto-plasmonic crystals. Moreover, we discuss how these coupling effects can be exploited to artificially enhance optical magnetism in plasmonic meta-molecules and crystals. Finally, we highlight some of the present challenges and provide a perspective on future directions of the research towards photon-driven fast and efficient nanotechnologies bridging magnetism and optics beyond current limits.

Pulses from a mid-infrared quantum cascade laser frequency comb using an external compressor

Matthew Singleton, Jérôme Faist, and Mattias Beck

Doc ID: 361328 Received 05 Mar 2019; Accepted 25 Apr 2019; Posted 26 Apr 2019  View: PDF

Abstract: A Martinez-type stretcher-compressor is used to modify the spectral phases of a high-power (~1 W) QCL comb emitted at 8.2 μm with more than 100 cm-1 spectral bandwidth. Using this scheme, we demonstrate a compression of the QCL output from a 134 ps continuous wave waveform, to a train of pulses of width 12 ps, and a power with peak to average ratio of 40.7. An evaluation of the phase noise of the free-running device yields an integrated timing jitter of 335 fs over the frequency range 20 KHz - 100 MHz, and a pulse to-pulse jitter of 2.0 fs, ultimately demonstrating the high phase stability of QCL combs through the tools commonly used by the ultrafast community.

Polarization dependent, plasmon-enhanced infrared transmission through gold nanoslits on monolayer black phosphorus

Guangsheng Deng, Xianglian Song, Koray Aydin, and Sina Abedini Dereshgi

Doc ID: 361355 Received 04 Mar 2019; Accepted 25 Apr 2019; Posted 13 May 2019  View: PDF

Abstract: Enhanced transmission is essential in many application cases. However, as an ordinary method to enhance wave transmission, traditional extraordinary transmission (EOT) based on nanohole array structures has no capability to widen its operation bandwidth. Here, we use a continuous monolayer black phosphorus (BP) film to enhance transmission through gold nanostructure arrays at mid-infrared (mid-IR) region. By exciting surface plasmon polaritons (SPPs) at the BP/gold nanostructure arrays interface, enhanced transmission over broad range of wavelengths was theoretically demonstrated. Using finite-difference time-domain (FDTD) simulations, we analyzed the effects of geometric parameters on the transmission spectra and demonstrated unique polarization-dependent transmission enhancement in BP/gold silt arrays and BP/gold patch arrays, which originates from the anisotropic properties of BP. Our work provides new guidance to the design of broadband, polarization-dependent extraordinary transmission enhancement.

Retrieval of the complex-valued refractive index of germanium near the M4,5 absorption edge

Christopher Kaplan, Peter Kraus, Eric Gullikson, Lauren Borja, Scott Cushing, Michael Zuerch, Hung-Tzu Chang, Daniel Neumark, and Stephen Leone

Doc ID: 362900 Received 22 Mar 2019; Accepted 24 Apr 2019; Posted 25 Apr 2019  View: PDF

Abstract: The complex valued index of refraction of germanium in the extreme ultraviolet (XUV) is measured by multi angle reflectance of synchrotron radiation. The resulting index of refraction is higher resolution than previously measured values. It reveals new structures attributed to transitions from the 3d core orbitals to the Σ5,2c and the X5,2c conduction bands. Additionally, it is shown that the problem of total external reflection, –which renders multi angle reflectance measurements insensitive to the complex-valued refractive index at grazing incidence, –can be overcome by employing measurements at angles of incidence away from the critical angle.

Active metamaterial nearly perfect light absorbers: a review [Invited]

Hodjat Hajian, Amir Ghobadi, Bayram Butun, and Ekmel Ozbay

Doc ID: 361230 Received 27 Feb 2019; Accepted 21 Apr 2019; Posted 22 Apr 2019  View: PDF

Abstract: Achieving nearly perfect light absorption from the microwave to optical region utilizing metamaterials has begun to play a significant role in photonics and optoelectronics due to their vital applications in thermal emitters, thermal photovoltaics, photovoltaics, sensing, filtering, and photodetection. However, employing passive components in designing perfect absorbers based on metamaterials and photonic crystals imposes some limits on their spectral operation. In order to overcome those limits, extensive research has been conducted on utilizing different materials and mechanisms to obtain active metamaterial light absorbers. In this review paper, we investigate the recent progresses in tunable and reconfigurable metamaterial light absorbers through reviewing different active materials and mechanisms, and we provide a perspective for their future development and applications.

Strong Light-Matter Coupling and Exciton-Polariton Condensation in Lattices of Plasmonic Nanoparticles

Mohammad Ramezani, Matthijs Berghuis, and Jaime Rivas

Doc ID: 360326 Received 19 Feb 2019; Accepted 16 Apr 2019; Posted 14 May 2019  View: PDF

Abstract: Arrays of metallic nanoparticles support collective plasmonic resonances known as surface lattice resonances (SLRs). The strong and delocalized electromagnetic fields associated to SLRs provide an excellent platform for experiments within the realm of light-matter interaction. The planar architecture of these arrays also provides a feasible system for coupling to different materials. One of the areas where SLRs have demonstrated their potential is strong light-matter coupling, with possible applications in nonlinear optics, coherent light generation, photochemistry and optoelectronics. In this perspective, we describe how SLRs are formed in arrays of plasmonic nanoparticles, introduce different materials used for strong coupling with SLRs, discuss some experiments that demonstrate the nonlinear emission of strongly coupled organic molecules with SLRs, and give our vision on future research directions of strongly coupled SLRs with organic molecules.

Relationship between morphology and transparency in glass-ceramic materials: comments

Mikhail Shepilov

Doc ID: 347430 Received 08 Oct 2018; Accepted 15 Mar 2019; Posted 17 May 2019  View: PDF

Abstract: Borrelli et al. [J. Opt. Soc. Am. B 35, 1725 (2018)] applied the approach of Debye and Bueche in discussion of light scattering in glass-ceramics. We show that the application is incorrect. We also demonstrate that the experimental example of Rayleigh wavelength dependence of turbidity of glass-ceramic presented by Borrelli et al. is unconvincing.

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