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Integrated Raman Laser: A Review of the Last Two Decades
摘要： Important accomplishments concerning an integrated laser source based on stimulated Raman scattering (SRS) have been achieved in the last two decades in the fields of photonics, microphotonics and nanophotonics. In 2005, the first integrated silicon laser based upon SRS was realized in the nonlinear waveguide. This breakthrough promoted an intense research activity addressed to the realization of integrated Raman sources in photonics microstructures, like microcavities and photonics crystals. In 2012, a giant Raman gain in silicon nanocrystals was measured for the first time. Starting from this impressive result, some promising devices have recently been realized combining nanocrystals and microphotonics structures. Of course, the development of integrated Raman sources has been influenced by the trend of photonics towards the nano-world, which started from the nonlinear waveguide, going through microphotonics structures, and finally coming to nanophotonics. Therefore, in this review, the challenges, achievements and perspectives of an integrated laser source based on SRS in the last two decades are reviewed, side by side with the trend towards nanophotonics. The reported results point out promising perspectives for integrated micro- and/or nano-Raman lasers.
关键词： nonlinear waveguide,lasers,microphotonics,nanophotonics,stimulated Raman scattering,optical microcavity,photonics crystals,nonlinear optics,nanocrystals
更新于2025-09-23 15:19:57
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Numerical modeling & analysis of AsSe2-As2S5 chalcogenide based step-index optical fiber for nonlinear applications
摘要： In this paper, we have proposed a chalcogenide-based step-index optical fiber with AsSe2 chalcogenide glass as core and As2S5 chalcogenide glass as cladding. It is designed and numerically analyzed for different values of radius of the core of the optical fiber. The chalcogenide-based step-index optical fiber, with a proposed value for its radius of the core, is then simulated for supercontinuum generation in the mid-infrared region by injecting an input pulse of 50 fs duration and peak power of 5000 W for different propagating lengths of the fiber.
关键词： As2S5 chalcogenide glass,Step-index optical fiber,AsSe2 chalcogenide glass,Nonlinear optics,Supercontinuum generation
更新于2025-09-23 15:19:57
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Deflecting transmissive light beams with metasurfaces based on crystalline silicon high-contrast grating
摘要： Dielectric metasurfaces have emerged and expanded rapidly for their success in realizing high-efficiency wavefront control in the optical and infrared ranges. However, devices have either been demonstrated at near-infrared regime using high-index semiconductors such as silicon, or they use lower index dielectric materials such as TiO2 or Si3N4 and operate in the visible wavelength regime to avoid the optical loss of dielectric materials. It seems that dielectric metasurfaces could not achieve either high index or high device efficiency, simultaneously. Here, we provide a crystalline silicon metasurface scheme to efficiently modulate transmitted light beams at the wavelengths as short as to 532 nm. The unit cell of the metasurfaces consists of high-contrast grating (HCG), which provides full 2π phase control for circular polarized incident beams in thin film. The demonstration of HCG deflector shows that the device enables high deflecting efficiency as high as those made by transparent materials. Our results provide a paradigm to functionalize transmitted light beams based on crystalline silicon in the visible wavelength regime.
关键词： dielectric metasurfaces,high-contrast grating,diffractive optics,crystalline silicon
更新于2025-09-23 15:19:57
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Coupling thermal atomic vapor to an integrated ring resonator
摘要： Strongly interacting atom–cavity systems within a network with many nodes constitute a possible realization for a quantum internet which allows for quantum communication and computation on the same platform. To implement such large-scale quantum networks, nanophotonic resonators are promising candidates because they can be scalably fabricated and interconnected with waveguides and optical fibers. By integrating arrays of ring resonators into a vapor cell we show that thermal rubidium atoms above room temperature can be coupled to photonic cavities as building blocks for chip-scale hybrid circuits. Although strong coupling is not yet achieved in this first realization, our approach provides a key step towards miniaturization and scalability of atom–cavity systems.
关键词： atom–cavity systems,ring resonators,integrated optics,atomic vapor spectroscopy
更新于2025-09-23 15:19:57
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[IEEE 2018 20th International Conference on Transparent Optical Networks (ICTON) - Bucharest (2018.7.1-2018.7.5)] 2018 20th International Conference on Transparent Optical Networks (ICTON) - All Dielectric Mode Order Transformation Photonic Structure Design by Evolutionary Optimization Approach
摘要： In this manuscript, an evolutionary algorithm is applied to design a mode order converter photonic crystal structure for achieving transformation of the propagating fundamental mode to the higher order mode. In order to transform incident light mode from an even mode to an odd mode, predefined mask object functions are employed. The cross-sectional field profiles at the output face of the optimized structure are utilized to evaluate the optimization cost function to achieve mode order transformation task. In the study, the optimized structure composed of dielectric alumina (Al2O3) rods and time domain analyses of the optimization process are done by using finite-difference time domain method. Furthermore, numerical results are confirmed by experiments for designed structure at the microwave frequencies. It is shown that the numerical calculations and experimental measurements agree well with each other.
关键词： mode order converter,differential evolution algorithm,phase shift,photonic crystals,integrated optics
更新于2025-09-23 15:19:57
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Demonstration of a Hybrid FSO/VLC Link for the Last Mile and Last Meter Networks
摘要： In this paper, a hybrid free-space optical and visible light communication (FSO/VLC) system was experimentally demonstrated as a solution to overcome the last mile and last meter access networks bandwidth bottleneck. We evaluate the system performance of a multiband carrier-less amplitude and phase (m-CAP) modulation scheme for a range of FSO/VLC link lengths and m-CAP parameters (i.e., the roll-off factor of the ?lters and a number of subcarriers) in terms of the data rate Rb (i.e., spectral ef?ciency). We show that for the con?guration with a 1 m VLC link the 10-CAP offers more than a 40 % improvement in the measured Rb compared to 2-CAP for the same bit error rate target. The Rb penalty due to the extension of a VLC link span from 1 m to 3 m reaches to 12.6 Mb/s for the 10-CAP scheme (i.e., ～39 % degradation in Rb). To fully cover all aspects of the hybrid FSO/VLC system, we also investigate the atmospheric turbulence effect on the 500 m FSO link n of 2.4×10?15 m?2/3 where Rb is decreased by 30 % for the refractive index structure parameter C2 compared to a clear channel condition.
关键词： multiband carrier-less amplitude and phase modulation,Visible light communication,free space optics
更新于2025-09-23 15:19:57
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Design of long period fiber grating surrounding refractive index sensor based on mode transition near phase-matching turning point
摘要： This work presents a novel design of long period fiber grating (LPFG) refractive index sensor based on mode transition near phase-matching turning point (PMTP). The dual peaks can approach to PMTP by adjusting the fiber radius, and LPFG can operate in the mode transition range by choosing the optimal film thickness. Through experiments, the LPFG based on mode transition near PMTP was fabricated by the aforesaid design, and a glycerol solution concentration monitoring test was performed to analyze its sensing properties. The results show that if the dual peaks are close to PMTP and the overlay thickness stays within the mode transition range, the sensitivity to surrounding refractive index (SRI) will be greatly improved. Compared with the regular LPFG sensors based on dual peaks resonance or the LPFG sensors based on mode transition, this LPFG has a higher sensitivity to SRI which can reach to 4900nm/RIU in the SRI range of 1.34~1.39.
关键词： Fiber optics,Thin films,Fiber optics sensors
更新于2025-09-19 17:15:36
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Atomic-Scale Characterization of Graphene p–n Junctions for Electron-Optical Applications
摘要： Graphene p-n junctions offer a potentially powerful approach towards controlling electron trajectories via collimation and focusing in ballistic solid-state devices. The ability of p-n junctions to control electron trajectories depends crucially on the doping profile and roughness of the junction. Here, we use four-probe scanning tunneling microscopy and spectroscopy (STM/STS) to characterize two state-of-the-art graphene p-n junction geometries at the atomic scale, one with CMOS polySi gates and another with naturally cleaved graphite gates. Using spectroscopic imaging, we characterize the local doping profile across and along the p-n junctions. We find that realistic junctions exhibit non-ideality both in their geometry as well as in the doping profile across the junction. We show that the geometry of the junction can be improved by using the cleaved edge of van der Waals metals such as graphite to define the junction. We quantify the geometric roughness and doping profiles of junctions experimentally and use these parameters in Nonequilibrium Green’s Function based simulations of focusing and collimation in these realistic junctions. We find that for realizing Veselago focusing, it is crucial to minimize lateral interface roughness which only natural graphite gates achieve, and to reduce junction width, in which both devices under investigation underperform. We also find that carrier collimation is currently limited by the non-linearity of the doping profile across the junction. Our work provides benchmarks of the current graphene p-n junction quality and provides guidance for future improvements.
关键词： graphene p-n junctions,collimation,Veselago lensing,scanning tunneling microscopy,solid state electron optics
更新于2025-09-19 17:15:36
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Estimating the Optical Properties of Inorganic Matter-Dominated Oligo-to-Mesotrophic Inland Waters
摘要： Many studies over the years have focused on bio-optical modeling of inland waters to monitor water quality. However, those studies have been conducted mainly in eutrophic and hyper-eutrophic environments dominated by phytoplankton. With the launch of the Ocean and Land Colour Instrument (OLCI)/Sentinel-3A in 2016, a range of bands became available including the 709 nm band recommended for scaling up these bio-optical models for productive inland waters. It was found that one category of existing bio-optical models, the quasi-analytical algorithms (QAAs), when applied to colored dissolved organic matter (CDOM) and detritus-dominated waters, produce large errors. Even after shifting the reference wavelength to 709 nm, the recently re-parameterized QAA versions could not accurately retrieve the inherent optical properties (IOPs) in waterbodies dominated by inorganic matter. In this study, three existing versions of QAA were implemented and proved inefficient for the study site. Therefore, several changes were incorporated into the QAA, starting with the re-parameterization of the empirical steps related to the total absorption coefficient retrieval. The re-parameterized QAA, QAAOMW showed a significant improvement in the mean absolute percentage error (MAPE). MAPE decreased from 58.05% for existing open ocean QAA (QAALv5) to 16.35% for QAAOMW. Considerable improvement was also observed in the estimation of the absorption coefficient of CDOM and detritus from a MAPE of 91.05% for QAALv5 to 18.87% for QAAOMW. The retrieval of the absorption coefficient of phytoplankton (aφ) using the native form of QAA proved to be inaccurate for the oligo-to-mesotrophic waterbody due to the low aφ returning negative predictions. Therefore, a novel approach based on the normalized aφ was adopted to maintain the spectral shape and retrieve positive values, resulting in an improvement of 119% in QAAOMW. Further tuning and scale-up of QAAOMW to OLCI bands will aid in monitoring water resources and associated watershed processes.
关键词： water quality,bio-optics,quasi-analytical algorithm,Brazilian reservoir,inland waters,inherent optical properties
更新于2025-09-19 17:15:36
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Broadband ultrafast nonlinear optical studies revealing exciting multi-photon absorption coefficients in phase pure zero-dimensional Cs <sub/>4</sub> PbBr <sub/>6</sub> perovskite films
摘要： Lead halide perovskite nanocrystals (NCs) apart from their overwhelming optoelectronic applications have recently demonstrated promising nonlinear optical (NLO) properties such as strong two-photon absorption cross-sections (～105 GM), two-photon fluorescence, and saturable absorption even at very high peak intensity. Zero-dimensional perovskite-related materials (0-D PRMs) are a new class of materials offering a high exciton binding energy (Eg ≥ 180 meV) with a strong photoluminescence (PL) quantum yield in few cases. Herein, we report the broadband third-order NLO properties of phase pure Cs4PbBr6 0-D PRM achieved using the Z-scan and degenerate four-wave mixing techniques in the femtosecond regime. Considering the growing content of the fluorescent and non-fluorescent forms of this material, we have performed our studies on both of them. These perovskite NCs exhibited strong multi-photon absorption properties in the near-infrared region with two-photon absorption (2PA) (cross-section, σ2 = 10?43–10?44 cm4 s equivalent to ～106 GM) in the 500–800 nm region, three-photon absorption (3PA) (cross-section, σ3 ～10?73 cm6 s2) in the 900–1200 nm region and four-photon absorption (4PA) (cross-section, σ4 ～10?100 cm8 s3) in the 1300–1500 nm spectral region. These multi-photon absorption processes are explained using a simple band diagram. The measured NLO coefficients and cross-sections are fairly large when compared to some of the earlier reports on perovskite-based NCs. Cs4PbBr6 0-D PRM also demonstrated a large third-order NLO susceptibility χ(3) (～10?7 esu), which can be attributed to the strong quantum confinement arising from spatially isolated, exciton containing individual [PbBr6]4? octahedron. These results clearly suggest the potential of 0D-PRMs in applications such as photonics and ultrafast all-optical switching devices.
关键词： Z-scan,perovskite nanocrystals,ultrafast optics,degenerate four-wave mixing,multi-photon absorption,nonlinear optical properties
更新于2025-09-19 17:15:36