- 标题
- 摘要
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- 实验方案
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An All-Optical, Actively Q-Switched Fiber Laser by an Antimonene-Based Optical Modulator
摘要： Q-switched ?ber lasers are of great interest in industrial material processing, nonlinear frequency conversion, spectroscopy etc. However, passive Q-switching possesses drawbacks of degradation and failure of the saturable absorber and the di?culty in accurate modi?cation of the repetition rate. To overcome these issues, active Q-switching that can normally modulate the cavity quality-factor by an externally-driven Q-switcher is in high demand. Herein, an actively Q-switched laser with antimonene-based all-optical modulator is devised based on the high photo-thermal e?ciency (48%) and broadband response in antimonene. It is demonstrated that this actively modulated laser represents all-optically tunable output parameters (e.g., output repetition rate), environmental stability, and easy synchronization. It is anticipated that this actively antimonene-based all-optical modulator with advantages of large modulation depth, low energy consumption, and high conversion e?ciency has great potential in all-optical information processing and pulsed laser engineering.
关键词： actively Q-switching,antimonene,2D materials,all-optical modulators
更新于2025-11-28 14:24:03
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Fast Calculation of Computer Generated Holograms for 3D Photostimulation through Compressive-Sensing Gerchberg–Saxton Algorithm
摘要： The use of spatial light modulators to project computer generated holograms is a common strategy for optogenetic stimulation of multiple structures of interest within a three-dimensional volume. A common requirement when addressing multiple targets sparsely distributed in three dimensions is the generation of a points cloud, focusing excitation light in multiple diffraction-limited locations throughout the sample. Calculation of this type of holograms is most commonly performed with either the high-speed, low-performance random superposition algorithm, or the low-speed, high performance Gerchberg–Saxton algorithm. This paper presents a variation of the Gerchberg–Saxton algorithm that, by only performing iterations on a subset of the data, according to compressive sensing principles, is rendered significantly faster while maintaining high quality outputs. The algorithm is presented in high-efficiency and high-uniformity variants. All source code for the method implementation is available as Supplementary Materials and as open-source software. The method was tested computationally against existing algorithms, and the results were confirmed experimentally on a custom setup for in-vivo multiphoton optogenetics. The results clearly show that the proposed method can achieve computational speed performances close to the random superposition algorithm, while retaining the high performance of the Gerchberg–Saxton algorithm, with a minimal hologram quality loss.
关键词： optogenetics,spatial light modulators,computer generated holograms
更新于2025-09-23 15:23:52
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Enhanced NRZ multi-carriers modulation technologies for microresonators in THz technology applications
摘要： Multi-optical carriers suitable for use in an optical communication system have been generated via integrated microring resonators. These carriers were sufficiently stable for travel in either a free space channel or waveguides while experiencing very low dispersion. Multiple carriers were created using the integrated microring resonators, with each carrier possessing a frequency at 193.012, 193.086, 193.186 and 193.268 terahertz (THz). The second part which is the non-return-to-zero (NRZ) modulation has been performed using the microring resonator modulators. The objective of the research is to generate multi-carriers at infrared region and modulate them for the optical communication application using the microring resonators. At the transmitter part, series of microring resonators have been used to generate four different THz frequencies which can be either de-multiplexed and modulated individually using the NRZ modulation format or modulated without de-multiplexing them as these enter a series of microring resonator modulators and microring resonator drop filters. As results, the detection of the four NRZ modulated frequencies has been performed successfully with high signal qualities. Therefore, in this research microring resonators are used for different purposes as to generate optical signals (at the transmitter part), modulate and filter them along an optical transmission link.
关键词： NRZ modulation,Microring drops,Microring modulators,Microring resonator
更新于2025-09-23 15:23:52
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Exceptional Points of Degeneracy Induced by Linear Time-Periodic Variation
摘要： We present a general theory of exceptional points of degeneracy (EPD) in periodically time-variant systems. We show that even a single resonator with a time-periodic component is able to develop EPDs, contrary to parity-time- (PT) symmetric systems that require two coupled resonators. An EPD is a special point in a system parameter space at which two or more eigenmodes coalesce in both their eigenvalues and eigenvectors into a single degenerate eigenmode. We demonstrate the conditions for EPDs to exist when they are directly induced by time-periodic variation of a system without loss and gain elements. We also show that a single resonator system with zero time-average loss-gain exhibits EPDs with purely real resonance frequencies, yet the resonator energy grows algebraically in time since energy is injected into the system from the time-variation mechanism. Although the introduced concept and formalism are general for any time-periodic system, here, we focus on the occurrence of EPDs in a single LC resonator with time-periodic modulation. These findings have significant importance in various electromagnetic and photonic systems and pave the way for many applications, such as sensors, amplifiers, and modulators. We show a potential application of this time-varying EPD as a highly sensitive sensor.
关键词： exceptional points of degeneracy,time-periodic systems,sensors,modulators,LC resonator,amplifiers
更新于2025-09-23 15:23:52
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Recent Trends in Compressive Raman Spectroscopy Using DMD-Based Binary Detection
摘要： The collection of high-dimensional hyperspectral data is often the slowest step in the process of hyperspectral Raman imaging. With the conventional array-based Raman spectroscopy acquiring of chemical images could take hours to even days. To increase the Raman collection speeds, a number of compressive detection (CD) strategies, which simultaneously sense and compress the spectral signal, have recently been demonstrated. As opposed to conventional hyperspectral imaging, where full spectra are measured prior to post-processing and imaging CD increases the speed of data collection by making measurements in a low-dimensional space containing only the information of interest, thus enabling real-time imaging. The use of single channel detectors gives the key advantage to CD strategy using optical filter functions to obtain component intensities. In other words, the filter functions are simply the optimized patterns of wavelength combinations characteristic of component in the sample, and the intensity transmitted through each filter represents a direct measure of the associated score values. Essentially, compressive hyperspectral images consist of 'score' pixels (instead of 'spectral' pixels). This paper presents an overview of recent advances in compressive Raman detection designs and performance validations using a DMD based binary detection strategy.
关键词： Chemometrics,multivariate data analysis,digital light processor (DLP),digital micromirror device (DMD),optimal binary filters,spatial light modulators (SLM),Raman spectroscopy,chemical imaging,compressive detection
更新于2025-09-23 15:22:29
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On-chip enhanced electro-optic Kerr effect for manipulation of optical orbital angular momentum modes
摘要： Mode Division Multiplexing (MDM) technique using higher order Orbital Angular Momentum (OAM) carrying modes through a channelized bandwidth provides enhanced capacity communication systems. Furthermore, encrypted channels via OAM based high-dimensional Quantum Key Distribution (QKD) improve the transmission rate and security. In such applications, mode-selective manipulation of the spatially distributed (here, OAM) modes is a significant function to implement MDM and QKD networks. This paper proposes a novel versatile-designed chip which is configured in a Ycut Periodically Poled Lithium Niobate (PPLN) photonic wire. This integrated optical device acts as spatial mode converter for data modulated on higher order OAM= ±2ˉh modes. The conversion is based on enhanced electro-optic (EO) Kerr effect via phase-mismatched cascaded polarization coupling interactions of decomposed guided modes in two successive PPLN sections. The high-purity (91%) and low-voltage (<14.6 V) of the proposed device enable its operation in compatible with applicable commercial modulators in OAM-based MDM and QKD systems.
关键词： Electro-optical devices,Integrated optics,Modulators,Singular optics
更新于2025-09-23 15:21:01
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Transmissive flexoelectro-optic liquid crystal optical phase modulator with 2 <b>??</b> modulation
摘要： In this paper, we demonstrate analog phase modulation in a transmissive configuration using the flexoelectro-optic effect in short-pitch chiral nematic liquid crystal (LC) devices. Two different modes are considered, both of which are shown to generate full 2π phase modulation at 1 kHz switching frequency. The first configuration that is considered consists of a half-wave plate that is placed between two flexoelectro-optic LC devices that are subjected to electric fields that are applied in phase. Second, we demonstrate that a similar phase modulation response can be observed by removing the half-wave plate and subjecting the two flexoelectro-optic LC devices to electric fields whereby the polarities are out of phase. Both configurations demonstrated herein are promising for the development of next-generation LC spatial light modulators, particularly when reflective geometries are challenging or impractical.
关键词： spatial light modulators,flexoelectro-optic effect,liquid crystal,phase modulation,transmissive configuration
更新于2025-09-23 15:21:01
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Study on void reduction in direct wafer bonding using Al <sub/>2</sub> O <sub/>3</sub> /HfO <sub/>2</sub> bonding interface for high-performance Si high- <i>k</i> MOS optical modulators
摘要： We have investigated the direct wafer bonding (DWB) method with a thin bonding dielectric interface to fabricate Si high-k MOS optical modulators with a thin equivalent oxide thickness (EOT). To suppress void generation on the bonded wafer during high-temperature annealing, we examined the high-k dielectric bonding interfacial layers, such as Al2O3 and HfO2. We found that the Al2O3/HfO2 bilayer enables void-less wafer bonding in conjunction with pre-bonding annealing at 700 °C. By using the 0.5-nm Al2O3/2.0-nm HfO2 bonding interface, the density of voids is reduced by three orders of magnitude as compared with that in the case of using the Al2O3 bonding interface. We achieved a density of voids of approximately 2 ' 10%3 cm%2 even when the bonded wafer is annealed at 700 °C. By thermal desorption spectroscopy (TDS), we found that degassing from the bonding interface is successfully suppressed by the introduction of the HfO2 layer and the pre-bonding annealing at 700 °C, which are considered to suppress void generation. Wafer bonding with thin Al2O3/HfO2 high-k bonding interface is promising for Si high-k MOS optical modulators.
关键词： Al2O3,void reduction,MOS optical modulators,high-k dielectric,HfO2,direct wafer bonding
更新于2025-09-23 15:21:01
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Tackling Performance Challenges in Organic Photovoltaics: An Overview about Compatibilizers
摘要： Organic Photovoltaics (OPVs) based on Bulk Heterojunction (BHJ) blends are a mature technology. Having started their intensive development two decades ago, their low cost, processability and flexibility rapidly funneled the interest of the scientific community, searching for new solutions to expand solar photovoltaics market and promote sustainable development. However, their robust implementation is hampered by some issues, concerning the choice of the donor/acceptor materials, the device thermal/photo-stability, and, last but not least, their morphology. Indeed, the morphological profile of BHJs has a strong impact over charge generation, collection, and recombination processes; control over nano/microstructural morphology would be desirable, aiming at finely tuning the device performance and overcoming those previously mentioned critical issues. The employ of compatibilizers has emerged as a promising, economically sustainable, and widely applicable approach for the donor/acceptor interface (D/A-I) optimization. Thus, improvements in the global performance of the devices can be achieved without making use of more complex architectures. Even though several materials have been deeply documented and reported as effective compatibilizing agents, scientific reports are quite fragmentary. Here we would like to offer a panoramic overview of the literature on compatibilizers, focusing on the progression documented in the last decade.
关键词： mixing interfaces,additives,bulk heterojunction,morphology modulators,donor/acceptor interface,organic photovoltaics,compatibilizers
更新于2025-09-23 15:21:01
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Electro-optical Amplitude and Phase Modulators Based on Tunable Guided-Mode Resonance Effect
摘要： Here, electrically tunable amplitude and phase modulators are designed by the hybridization of indium tin oxide (ITO) into a guided-mode resonance mirror (so-called GMRM) which consists of a high-index silicon (Si) nanograting placed on top of a Si guiding core followed by a silicon-dioxide optical buffer layer and a highly reflective substrate. The physical mechanism is based on the intriguing optical characteristics of GMRMs and integration of a dual-gated ITO with the capability of charge carrier modulation into the Si nanograting. A gate-tunable amplitude modulator with a modulation depth as high as ≈0.80 is realized by careful selection of structural parameters, excitation of a strongly coupled guided-mode resonance, and modifying the external bias voltage. This design can also be adjusted only by changing the thickness of its optical buffer layer and moderating the strength of the guided-mode resonance to serve as an efficient active phase modulator. The phase variation of ≈210° and relatively high reflection amplitude in 0.45-0.6 range are accomplished when the applied bias voltage alters from -15 V to +24 V. This reflection phase tuning mainly originates from the carrier depletion and accumulation inside the incorporated 5 nm-thick ITO layer. The accurate modeling and numerical calculation of optical response of the proposed unit cell for different applied external voltages are carried out through linking the electrostatics device physics model and rigorous coupled wave analysis (RCWA) optical simulation. The design rules and physical principles behind the dual-gated ITO-integrated GMRM unit cell are discussed in-depth by investigation of the structural parameters, the nature of supported resonances, and voltage-dependent effects of inhomogeneous carrier distributions in both ITO and Si layers. The electrical addressability and individual control over pixelated subwavelength unit cells provide the opportunity for realizing an actively reconfigurable metasurface with the desired gradient phase delay.
关键词： metasurfaces,phase and amplitude modulators,electro-optical materials,silicon,guided-mode resonance,indium tin oxide,All-dielectric
更新于2025-09-23 15:19:57