查看更多>>摘要：Optical Vortex arrays,with their unique wavefront structures,find extensive applications in fields such as optical commu-nications,trapping,imaging,metrology,and quantum.The methods used to generate these vortex beam arrays are crucial for their applications.In this review,we begin with introducing the fundamental concepts of optical vortex beams.Subsequently,we present three methods for generating them,including diffractive optical elements,metasurfaces,and integrated optical devices.We then explore the applications of optical vortex beam arrays in five different domains.Finally,we conclude with a summary and outlook for the research on optical vortex beam arrays.
查看更多>>摘要：Modern scintillator-based radiation detectors require silicon photomultipliers[SiPMs]with photon detection efficiency higher than 40％at 420 nm,possibly extended to the vacuum ultraviolet[VUV]region,single-photon time resolution[SPTR]＜100 ps,and dark count rate[DCR]＜150 kcps/mm2.To enable single-photon time stamping,digital electronics and sensitive microcells need to be integrated in the same CMOS substrate,with a readout frame rate higher than 5 MHz for arrays extending over a total area up to 4 mm × 4 mm.This is challenging due to the increasing doping concentrations at low CMOS scales,deep-level carrier generation in shallow trench isolation fabrication,and power consumption,among others.The advances at 350 and 110 nm CMOS nodes are benchmarked against available SiPMs obtained in CMOS and commercial customized technologies.The concept of digital multithreshold SiPMs with a single microcell readout is finally reported,proposing a possible direction toward fully digital scintillator-based radiation detectors.
查看更多>>摘要：On-chip stimulated Brillouin scattering[SBS]has attracted extensive attention by introducing acousto-optic coupling inter-actions in all-optical signal processing systems.A series of chip-level applications such as Brillouin lasers,amplifiers,gyro-scopes,filters,and nonreciprocal devices are realized based on Brillouin acousto-optic interaction.Here,we first introduce the fundamental principle of SBS in integrated photonics and a method for calculating Brillouin gain;then we illustrate the Brillouin effect on different material platforms with diverse applications.Finally,we make a concise conclusion and offer prospects on the future developments of on-chip SBS.
查看更多>>摘要：In recent years,optical phased arrays[OPAs]have attracted great interest for their potential applications in light detection and ranging[LiDAR],free-space optical communications[FSOs],holography,and so on.Photonic integrated circuits[PICs]provide solutions for further reducing the size,weight,power,and cost of OPAs.In this paper,we review the recent develop-ment of photonic integrated OPAs.We summarize the typical architecture of the integrated OPAs and their performance.We analyze the key components of OPAs and evaluate the figure of merit for OPAs.Various applications in LiDAR,FSO,imaging,biomedical sensing,and specialized beam generation are introduced.
查看更多>>摘要：We propose a scheme that utilizes weak-field-induced quantum beats to investigate the electronic coherences of atoms driven by a strong attosecond extreme ultraviolet[XUV]pulse.The technique involves using a strong XUV pump pulse to excite and ionize atoms and a time-delayed weak short pulse to probe the photoelectron signal.Our theoretical analysis demonstrates that the information regarding the bound states,initiated by the strong pump pulse,can be precisely recon-structed from the weak-field-induced quantum beat spectrum.To examine this scheme,we apply it to the attosecond XUV laser-induced ionization of hydrogen atoms by solving a three-dimensional time-dependent Schrödinger equation.This work provides an essential reference for reconstructing the ultrafast dynamics of bound states induced by strong XUV atto-second pulses.
查看更多>>摘要：In this work,we compare different methods for implementing a triplicator,a phase grating that generates three equi-intense diffraction orders.The design with optimal efficiency features a continuous phase profile,which cannot be easily reproduced,and is typically affected by quantization.We compare its performance with binary and sinusoidal phase pro-files.We also analyze the effect of quantizing the phase levels.Finally,a random approach is adopted to eliminate the additional harmonic orders.In all cases,a liquid-crystal-on-silicon spatial light modulator is employed to experimentally verify and compare the different approaches.
查看更多>>摘要：In order to alleviate the impact of turbulence on the performance of underwater wireless optical communication[UWOC]in real time,and achieve high-speed real-time transmission and low cost and miniaturization of equipment,a 2 × 2 real-time multiple-input and multiple-output[MIMO]high-speed miniaturized UWOC system based on a field-programmable gate array[FPGA]and a high-power light-emitting diode[LED]array is designed in this Letter.In terms of multiplexing gain,the imaging MIMO spatial multiplexing and high-order modulation for the first time are combined and the real-time high-speed transmission of PAM-4 signal based on the LED array light source in 12 m underwater channel at 100 Mbps rate is implemented,which effectively improves the throughput of the UWOC system with a high-power commercial LED light source.In light of diversity gain,the system employs the diversity of repeated coding scheme to receive two identical non-return-to-zero on-off keying[NRZ-OOK]signals,which can compensate the fading or flickering sublinks in real time under the bubble-like simulated turbulence condition,and has high robustness.To our knowledge,this is the first instance of a high rate and long-distance implementation of a turbulence-resistant real-time MIMO miniaturized UWOC system based on FPGA and high-power LED arrays.With spatial diversity or spatial multiplexing capabilities,its low cost,integrity,and high robustness provide the system with important practical prospects.
查看更多>>摘要：We introduce an all-optical approach,optical parametric amplification[OPA]processor to suppress the impact of Sun out-age in laser satellite communication systems,which is implemented by only one nonlinear semiconductor optical amplifier driven by both electrical and optical pumps.The optimized OPA processor,with a current of 539 mA and a pump-to-signal ratio of 16 dB,could significantly improve the signal quality by 3.5 dB in experiments for the elevation angle of Sun radiation of 0 rad.The signal quality improvement is observed in the whole range of the elevation angle,confirming the effectiveness of the proposed OPA processor in the field of Sun radiation mitigation.
查看更多>>摘要：In this Letter,we propose and experimentally demonstrate a lens-free wavefront shaping method that utilizes synchronized signal block beam alignment and a genetic algorithm[SSBGA]for a diffuse non-line-of-sight[NLOS]visible light commu-nication[VLC]system.The proposed method effectively controls the position and mobility of visible light beams by partitioning spatial light modulator pixels and manipulating beams to converge at distinct spatial positions,thereby enhanc-ing wavefront shaping efficiency,which achieves a significant 23.9 dB optical power enhancement at+2 mm offset,sur-passing the lens-based continuous sequence[CS]scheme by 21.7 dB.At+40° angle,the improvement reaches up to 11.8 dB and 16.8 dB compared to the results with and without lens-based CS,respectively.A maximum rate of 5.16 Gbps is success-fully achieved using bit-power loading discrete multi-tone[DMT]modulation and the proposed SSBGA in an NLOS VLC sys-tem,which outperforms the lens-based CS by 1.07 Gbps and obtains a power saving of 55.6％during the transmission at 4 Gbps.To the best of our knowledge,this is the first time that high-speed communication has been realized in an NLOS VLC system without a lens.
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