2022, 10(8) Column
Spectroscopy Nanophotonics and Photonic Crystals Errata Silicon Photonics Image Processing and Image Analysis Lasers and Laser Optics Instrumentation and Measurements Integrated Optics Optoelectronics Fiber Optics and Optical Communications Imaging Systems, Microscopy, and Displays Quantum Optics Optical Devices Nonlinear Optics Ultrafast Optics Optical Metasurfaces: Fundamentals and Applications
Photonics Research 第10卷 第8期
Lamb-dip saturated-absorption cavity ring-down rovibrational molecular spectroscopy in the near-infrared
The high-detection-sensitivity saturated-absorption cavity ring-down (SCAR) technique is extended to Lamb-dip spectroscopy of rovibrational molecular transitions in the near-infrared region. Frequency-comb-referenced sub-Doppler saturation measurements, performed on the acetylene
R(14)e line at , are analyzed by a SCAR global line profile fitting routine, based on a specially developed theoretical model. Compared to a conventional cavity ring-down evaluation, our approach yields dip profiles with a linewidth freed from saturation broadening effects, reduced by 40%, and a signal-to-noise ratio increased by 90%. Ultimately, an overall (statistical and systematic) fractional uncertainty as low as is achieved for the absolute line-center frequency. At the same time, our method is also able to accurately infer the linear (non-saturated) behavior of the gas absorption, providing Lamb-dip-based line strength measurements with a relative uncertainty of 0.5%.
Tunable coupled mechanical resonators with nonequilibrium dynamic phenomena have attracted considerable attention in quantum simulations, quantum computations, and non-Hermitian systems. In this study, we propose tunable mechanical-mode coupling based on nanobeam-double optomechanical cavities. The excited optical mode interacts with both symmetric and antisymmetric mechanical supermodes and mediates coupling at a frequency of approximately 4.96 GHz. The mechanical-mode coupling is tuned through both optical spring and gain effects, and the reduced coupled frequency difference in non-Hermitian parameter space is observed. These results benefit research on the microscopic mechanical parity–time symmetry for topology and on-chip high-sensitivity sensors.
Recently studied bound states in the continuum (BICs) enable perfect localization of light and enhance light–matter interactions although systems are optically open. They have found applications in numerous areas, including optical nonlinearity, light emitters, and nano-sensors. However, their unidirectional nature in nonreciprocal devices is still elusive because such trapping states are easily destroyed when the symmetry of an optical system is broken. Herein, we propose nonreciprocal and dynamically tunable BICs for unidirectional confinement of light and symmetry-protected BICs at
-point by introducing antiparallel magnetism into the optical system. We demonstrate that such BICs can be achieved by using topological magnetic Weyl semimetals near zero-index frequency without any structural asymmetry, and are largely tunable via modifying the Fermi level. Our results reveal a regime of extreme light manipulation and interaction with emerging quantum materials for various practical applications.
Time shifting deviation method enhanced laser interferometry: ultrahigh precision localizing of traffic vibration using an urban fiber link: publisher’s note
This publisher’s note corrects the title in
. 10, 433 ( 2022) 10.1364/PRJ.443019
Quantum dot lasers on silicon have gained significant interest over the past decade due to their great potential as an on-chip silicon photonic light source. Here, we demonstrate multi-wavelength injection locking of InAs/GaAs quantum dot Fabry–Perot (FP) lasers both on GaAs and silicon substrates by optical self-injection via an external cavity. The number of locked laser modes can be adjusted from a single peak to multiple peaks by tuning wavelength dependent phase and mode spacing of back-injected light through a Lyot filter. The multi-wavelength injection locked laser modes exhibit average optical linewidth of
, which are narrowed by approximately three orders of magnitude from their free-running condition. Furthermore, multi-wavelength self-injection locking via an external cavity exhibits flat-top optical spectral properties with approximately 30 stably locked channels under stable operation over time, where the frequency detuning is less than 700 MHz within 40 min. Particularly, FP lasers by direct epitaxial growth on silicon substrates are self-injection locked as a flat-top comb source with tunable free spectral range from approximately 25 to 700 GHz. The reported results emphasize the great potential of multi-wavelength injection locked lasers as tunable on-chip multi-wavelength light sources.
Snapshot spectral compressive imaging reconstruction using convolution and contextual TransformerDownload：502次
Spectral compressive imaging (SCI) is able to encode a high-dimensional hyperspectral image into a two-dimensional snapshot measurement, and then use algorithms to reconstruct the spatio-spectral data-cube. At present, the main bottleneck of SCI is the reconstruction algorithm, and state-of-the-art (SOTA) reconstruction methods generally face problems of long reconstruction times and/or poor detail recovery. In this paper, we propose a hybrid network module, namely, a convolution and contextual Transformer (CCoT) block, that can simultaneously acquire the inductive bias ability of convolution and the powerful modeling ability of Transformer, which is conducive to improving the quality of reconstruction to restore fine details. We integrate the proposed CCoT block into a physics-driven deep unfolding framework based on the generalized alternating projection (GAP) algorithm, and further propose the GAP-CCoT network. Finally, we apply the GAP-CCoT algorithm to SCI reconstruction. Through experiments on a large amount of synthetic data and real data, our proposed model achieves higher reconstruction quality (
in peak signal-to-noise ratio on simulated benchmark datasets) and a shorter running time than existing SOTA algorithms by a large margin. The code and models are publicly available at https://github.com/ucaswangls/GAP-CCoT.
Repetition rate locked single-soliton microcomb generation via rapid frequency sweep and sideband thermal compensation
Dissipative Kerr solitons (DKSs) with mode-locked pulse trains in high-
optical microresonators possess low-noise and broadband parallelized comb lines, having already found plentiful cutting-edge applications. However, thermal bistability and thermal noise caused by the high microresonator power and large temperature exchange between microresonator and the environment would prevent soliton microcomb formation and deteriorate the phase and frequency noise. Here, a novel method that combines rapid frequency sweep with optical sideband thermal compensation is presented, providing a simple and reliable way to get into the single-soliton state. Meanwhile, it is shown that the phase and frequency noises of the generated soliton are greatly reduced. Moreover, by closing the locking loop, an in-loop repetition rate fractional instability of at 1 s integration time and a triangular linear repetition rate sweep with 2.5 MHz could be realized. This demonstration provides a means for the generation, locking, and tuning of a soliton microcomb, paving the way for the application of single-soliton microcombs in low-phase-noise microwave generation and laser ranging.
Generalized robust training scheme using genetic algorithm for optical neural networks with imprecise components
One of the pressing issues for optical neural networks (ONNs) is the performance degradation introduced by parameter uncertainties in practical optical components. Hereby, we propose a novel two-step
ex situ training scheme to configure phase shifts in a Mach–Zehnder-interferometer-based feedforward ONN, where a stochastic gradient descent algorithm followed by a genetic algorithm considering four types of practical imprecisions is employed. By doing so, the learning process features fast convergence and high computational efficiency, and the trained ONN is robust to varying degrees and types of imprecisions. We investigate the effectiveness of our scheme by using practical machine learning tasks including Iris and MNIST classifications, showing more than 23% accuracy improvement after training and accuracy (90.8% in an imprecise ONN with three hidden layers and 224 tunable thermal-optic phase shifters) comparable to the ideal one (92.0%).
Dissipative Kerr soliton generation in chip-scale nonlinear resonators has recently observed remarkable advances, spanning from massively parallel communications, to self-referenced oscillators, and to dual-comb spectroscopy. Often working in the anomalous dispersion regime, unique driving protocols and dispersion in these nonlinear resonators have been examined to achieve the soliton and soliton-like temporal pulse shapes and coherent frequency comb generation. The normal dispersion regime provides a complementary approach to bridge the nonlinear dynamical studies, including the possibility of square pulse formation with flattop plateaus, or platicons. Here we report observations of square pulse formation in chip-scale frequency combs through stimulated pumping at one free spectral range and in silicon nitride rings with
normal group velocity dispersion. Tuning of the platicon frequency comb via a varied sideband modulation frequency is examined in both spectral and temporal measurements. Determined by second-harmonic autocorrelation and cross correlation, we observe bright square platicon pulse of 17 ps pulse width on a 19 GHz flat frequency comb. With auxiliary-laser-assisted thermal stabilization, we surpass the thermal bistable dragging and extend the mode-locking access to narrower 2 ps platicon pulse states, supported by nonlinear dynamical modeling and boundary limit discussions.
Recently, lead-free all-inorganic halide perovskites have attracted great interest because they not only have the merits of the halide perovskite family, but also are non-toxic. However, the commercialization of lead-free all-inorganic perovskites is restricted by their relatively low performances, which are usually caused by the fabrication methods and undesirable interfaces between the active layer and carrier transport layers. Herein, we demonstrate a solution-processed route for high-quality
lead-free perovskite film by adopting ideal electron transport material and a carbon electrode. By optimizing the fabrication process and tailoring the composition of the perovskite active layer, a high-performance photodetector (PD) with an structure PD is first fabricated, which shows good self-powered performance with a detectivity of as high as Jones and a linear dynamic range of up to 138 dB, which are better than those of the reported Pb-free perovskite PDs and comparable to high-performance Pb-based perovskite PDs. In addition, our unpackaged PDs show good light, thermal, and storage stability in air. Our results provide a special route for the development of lead-free perovskite devices in an environmentally friendly field.
High-speed long-distance visible light communication based on multicolor series connection micro-LEDs and wavelength division multiplexing
Multicolor series connection micro-LED arrays with emission wavelengths of violet, blue, green, and yellow were fabricated, and their optoelectronic properties and communication performances were investigated. The designed series connection micro-LED array exhibited the light output power of multiple milliwatts, whereas mostly keeping a slightly reduced modulation bandwidth, thus, enabling a higher signal-to-noise ratio compared to a single pixel and showing superior performance in the field of long-distance visible light communication (VLC). The achievable data rates of 400-, 451-, 509-, and 556-nm micro-LED arrays using bit/power loading orthogonal frequency division multiplexing were 5.71, 4.86, 4.39, and 0.82 Gbps, respectively. The aggregate data rate of 15.78 Gbps was achieved for the proof-of-concept wavelength division multiplexing system under a transmission distance of 13 m, which was the best data rate-distance product performance for the LED-based VLC to the best of our knowledge. In addition, the long-distance VLC based on yellow micro-LED was also demonstrated for the first time in this paper.
Imaging ultrafast evolution of subwavelength-sized topography using single-probe structured light microscopy
Imaging ultrafast processes in femtosecond (fs) laser–material interactions such as fs laser ablation is very important to understand the physical mechanisms involved. To achieve this goal with high resolutions in both spatial and temporal domains, a combination of optical pump–probe microscopy and structured illumination microscopy can be a promising approach, but suffers from the multiple-frame method with a phase shift that is inapplicable to irreversible ultrafast processes such as ablation. Here, we propose and build a wide-field single-probe structured light microscopy (SPSLM) to image the ultrafast three-dimensional topography evolution induced by fs lasers, where only a single imaging frame with a single structured probe pulse is required for topography reconstruction, benefiting from Fourier transform profilometry. The second harmonic of the fs laser is used as the structured probe light to improve spatial lateral resolution into the subwavelength region of
, and the spatial axial and temporal resolutions are estimated to be and , respectively. With SPSLM, we successfully image the ultrafast topography evolution of a silicon wafer surface impacted by single and multiple fs pulses. The variable formation and evolution of the laser induced periodic surface structures during an ultrashort time are visualized and analyzed. We believe that SPSLM will be a significant approach for revealing and understanding various ultrafast dynamics, especially in fs laser ablation and material science.
Quantum teleportation is a key primitive across a number of quantum information tasks and represents a fundamental ingredient for many quantum technologies. Channel capacity, other than the fidelity, becomes another focus of quantum communication. Here, we present a 5-channel multiplexing continuous-variable quantum teleportation protocol in the optical frequency comb system, exploiting five-order entangled sideband modes. Because of the resonant electro-optical modulation (EOM) that is specifically designed, the fidelities of five channels are greater than 0.78, which are superior to the no-cloning limit of
. This work provides a feasible scheme for implementing efficient quantum information processing.
Observation of parity-time symmetry in time-division multiplexing pulsed optoelectronic oscillators within a single resonator
In recent years, parity-time (PT) symmetry in optoelectronic systems has been widely studied, due to its potential applications in lasers, sensors, topological networks, and other fields. In this paper, a time-division multiplexed pulsed optoelectronic oscillator (OEO) is proposed to study the dynamics of a PT symmetry system. Two microwave pulses are used to realize the PT symmetry in a single spatial resonator based on the temporal degrees of freedom. The gain and loss of the microwave pulses and the coupling coefficient between them can then be controlled. We first demonstrate the phase diagram from PT broken to PT symmetry in the OEO system. We theoretically prove that the perturbation of a coupling-induced phase shift larger than
causes the disappearance of the PT symmetry. In this experiment, the perturbation is less than ; thus, the phase transition of PT symmetry is observed. In addition, multipairs of PT-symmetry pulses indicate that pulsed OEO could be used to implement complex non-Hermitian Hamilton systems. Therefore, it is confirmed that pulsed OEO is an excellent platform to explore the dynamics of PT symmetry and other non-Hermitian Hamiltonian systems.
Superoscillation metalenses have demonstrated promising prospects in breaking the theoretical diffraction limitations on the resolution of optical devices and systems. However, most reported superoscillation metalenses have a very small field of view of several tenths of a degree, which greatly limits their applications in imaging and microscopy. Therefore, it is of critical importance to achieve absolute high resolution by increasing the numerical apertures (NAs) of optical devices and systems. Unfortunately, similar to the case in traditional optics, it is challenging to realize a large field of view at high NA, especially in the superoscillation regime. To date, no attempt has been made to achieve flat-field focusing in the superoscillation regime, to our knowledge. Here, we demonstrate a high-NA superoscillation metalens with an entrance aperture stop, which is optimized for superoscillation performance with a comparatively large field of view. The proposed flat-field superoscillation metalens has an effective NA as large as 0.89 and achieves superoscillation focusing within a field of view of 9°. Such a superoscillation metalens may offer a promising way toward superoscillation imaging and fast-scanning label-free far-field superoscillation microscopy.
Microresonator-based optical frequency combs are broadband light sources consisting of equally spaced and coherent narrow lines, which are extremely promising for applications in molecular spectroscopy and sensing in the mid-infrared (MIR) spectral region. There are still great challenges in exploring how to improve materials for microresonator fabrication, extend spectral bandwidth of parametric combs, and realize fully stabilized soliton MIR frequency combs. Here, we present an effective scheme for broadband MIR optical frequency comb generation in a
crystalline microresonator pumped by the quantum cascade laser. The spectral evolution dynamics of the MIR Kerr frequency comb is numerically investigated, revealing the formation mechanism of the microresonator soliton comb via scanning the pump-resonance detuning. We also experimentally implement the modulation instability state MIR frequency comb generation in resonators covering from 3380 nm to 7760 nm. This work proceeds microresonator-based comb technology toward a miniaturization MIR spectroscopic device that provides potential opportunities in many fields such as fundamental physics and metrology.
Classic interferometry was commonly adopted to realize ultrafast phase imaging using pulsed lasers; however, the reference beam required makes the optical structure of the imaging system very complex, and high temporal resolution was reached by sacrificing spatial resolution. This study presents a type of single-shot ultrafast multiplexed coherent diffraction imaging technique to realize ultrafast phase imaging with both high spatial and temporal resolutions using a simple optical setup, and temporal resolution of nanosecond to femtosecond scale can be realized using lasers of different pulse durations. This technique applies a multiplexed algorithm to avoid the data division in space domain or frequency domain and greatly improves the spatial resolution. The advantages of this proposed technique on both the simple optical structure and high image quality were demonstrated by imaging the generation and evaluating the laser-induced damage and accompanying phenomenon of laser filament and shock wave at a spatial resolution better than 6.96 μm and a temporal resolution better than 10 ns.
Realizing fast temperature measurement and simulating Maxwell’s demon with nearly nondestructive detection in cold atoms
Optical detection and manipulation of the thermal properties is an essential subject of cold atoms in the quantum era. For laser cooled alkali atoms, we have experimentally realized deterministic temperature measurement with time cost below 1 ms and effective filtering of colder atoms with temperature less than 1 μK, with the help of nearly nondestructive detection. The quick temperature measurement is accomplished by carefully resolving the diffusion dynamics of atoms with the information provided by a single probe laser pulse in the form of bucket detection, while suppressing the amplitude and phase noises of probe laser. The separation of colder atoms is attainable as the velocity differences of atoms translate into nontrivial position differences, when the diffusion sustains for a few tens of milliseconds. In particular, these efforts are based on a labeling process that distinguishes the cold atoms under study from the others by specific internal states, while the nearly nondestructive detection is implemented via driving a cycling transition with continuous optical pulses. Moreover, such a position-dependent labeling process can be further modified to become velocity-dependent, with which we have demonstrated a Maxwell’s demon-type operation on cold atoms, as Maxwell’s demon’s intricate abilities can be understood as measuring the velocity of an individual particle and then performing feedback according to a straightforward dichotomy of the velocity value.
Three-terminal germanium-on-silicon avalanche photodiode with extended p-charge layer for dark current reduction
Germanium-on-silicon (Ge-on-Si) avalanche photodiodes (APDs) are widely used in near-infrared detection, laser ranging, free space communication, quantum communication, and other fields. However, the existence of lattice defects at the Ge/Si interface causes a high dark current in the Ge-on-Si APD, degrading the device sensitivity and also increasing energy consumption in integrated circuits. In this work, we propose a novel surface illuminated Ge-on-Si APD architecture with three terminals. Besides two electrodes on Si substrates, a third electrode is designed for Ge to regulate the control current and bandwidth, achieving multiple outputs of a single device and reducing the dark current of the device. When the voltage on Ge is
, the proposed device achieves a dark current of 100 nA, responsivity of 9.97 A/W at input laser power at 1550 nm, and optimal bandwidth of 142 MHz. The low dark current and improved responsivity can meet the requirements of autonomous driving and other applications demanding weak light detection.
In this work, a novel ultrafast optoelectronic proximity sensor based on a submillimeter-sized GaN monolithic chip is presented. Fabricated through wafer-scale microfabrication processes, the on-chip units adopting identical InGaN/GaN diode structures can function as emitters and receivers. The optoelectronic properties of the on-chip units are thoroughly investigated, and the ability of the receivers to respond to changes in light intensity from the emitter is verified, revealing that the sensor is suitable for operation in reflection mode. Through a series of dynamic measurements, the sensor is highly sensitive to object movement at subcentimeter distances with high repeatability. The sensor exhibits ultrafast microsecond response, and its real-time monitoring capability is also demonstrated by applying it to detect slight motions of moving objects at different frequencies, including the human heart rate, the vibration of the rotary pump, the oscillation of the speaker diaphragm, and the speed of the rotating disk. The compact and elegant integration scheme presented herein opens a new avenue for realizing a chip-scale proximity sensing device, making it a promising candidate for widespread practical applications.
Heterogeneously integrated quantum-dot emitters efficiently driven by a quasi-BIC-supporting dielectric nanoresonator
Bound states in the continuum (BICs) can make subwavelength dielectric resonators sustain low radiation leakage, paving a new way to minimize the device size, enhance photoluminescence, and even realize lasing. Here, we present a quasi-BIC-supporting GaAs nanodisk with embedded InAs quantum dots as a compact bright on-chip light source, which is realized by heterogeneous integration, avoiding complex multilayered construction and subsequent mismatch and defects. The emitters are grown inside the nanodisk to match the mode field distribution to form strong light–matter interaction. One fabricated sample demonstrates a photoluminescence peak sustaining a quality factor up to 68 enhanced by the quasi-BIC, and the emitting effect can be further promoted by improving the epilayer quality and optimizing the layer-transferring process in the fabrication. This work provides a promising solution to building an ultracompact optical source to be integrated on a silicon photonic chip for high-density integration.
Image data acquired with fused multispectral information can be used for effective identification and navigation owing to additional information beyond human vision, including thermal distribution, night vision, and molecular composition. However, the construction of photodetectors with such capabilities is hindered by the structural complexity arising from the integration of multiple semiconductor junctions with distinct energy gaps and lattice constants. In this work, we develop a colloidal quantum-dot dual-mode detector capable of detecting, separating, and fusing photons from various wavelength ranges. Using three vertically stacked colloidal quantum-dot homojunctions with alternating polarity, single-band short-wave infrared imaging and fused-band imaging (short-wave and mid-wave infrared) can be achieved with the same detector by controlling bias polarity and magnitude. The dual-mode detectors show detectivity up to
Jones at the fused-band mode and Jones at the single-band mode, respectively. Without image post-processing algorithms, the dual-mode detectors could provide both night vision and thermal information-enhanced night vision imaging capability. To the best of our knowledge, this is the first colloidal quantum-dot detector that can achieve such functionality. The operation mode can be changed at a high frequency up to 1.7 MHz, making it possible to achieve simultaneously dual-mode imaging and remote temperature sensing.
Ultrathin oxide controlled photocurrent generation through a metal–insulator–semiconductor heterojunction
Recent advances in nanoscale lasers, amplifiers, and nonlinear optical converters have demonstrated the unprecedented potential of metal–insulator–semiconductor (MIS) structures as a versatile platform to realize integrated photonics at the nanoscale. While the electric field enhancement and confinement have been discussed intensively in MIS based plasmonic structures, little is known about the carrier redistribution across the heterojunction and photocurrent transport through the oxide. Herein, we investigate the photo-generated charge transport through a single CdSe microbelt-
-Ag heterojunction with oxide thickness varying from 3 nm to 5 nm. Combining photocurrent measurements with finite element simulations on electron (hole) redistribution across the heterojunction, we are able to explain the loss compensation observed in hybrid plasmonic waveguides at substantially reduced pump intensity based on MIS geometry compared to its photonic counterpart. We also demonstrate that the MIS configuration offers a low-dark-current photodetection scheme, which can be further exploited for photodetection applications.
Bright single-photon sources in the telecom band by deterministically coupling single quantum dots to a hybrid circular Bragg resonator
High-performance solid-state quantum sources in the telecom band are of paramount importance for long-distance quantum communications and the quantum Internet by taking advantage of a low-loss optical fiber network. Here, we demonstrate bright telecom-wavelength single-photon sources based on In(Ga)As/GaAs quantum dots (QDs) deterministically coupled to hybrid circular Bragg resonators (h-CBRs) by using a wide-field fluorescence imaging technique. The QD emissions are redshifted toward the telecom O-band by using an ultra-low InAs growth rate and an InGaAs strain reducing layer. Single-photon emissions under both continuous wave (CW) and pulsed operations are demonstrated, showing high brightness with count rates of 1.14 MHz and 0.34 MHz under saturation powers and single-photon purities of
(CW) and (pulsed) at low excitation powers. A Purcell factor of 4.2 with a collection efficiency of at the first lens is extracted, suggesting efficient coupling between the QD and h-CBR. Our work contributes to the development of highly efficient single-photon sources in the telecom band for fiber-based quantum communication and future distributed quantum networks.
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