- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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Extremely high-brightness tapered photonic crystal diode laser with narrow-emitting aperture
摘要： High-brightness tapered photonic crystal diode lasers in the 980 nm range are investigated. The tapered lasers with a 20 μm wide light-emitting aperture achieved 2.55 W at 3.2 A. The beam quality factor M2 in the vertical and lateral directions are 1.16 and 1.48 at 2.5 A. Maximum brightness ?2 · sr at the second moment level is achieved. The devices also shows a narrow far-field of 17.1° × 6.5° in the vertical and lateral directions and a high efficiency of 53%. The proportion of the first-order mode in the lasing emission is also investigated based on the measured beam quality factor.
关键词： high-brightness,beam quality factor,far-field,tapered photonic crystal diode laser,narrow-emitting aperture
更新于2025-09-11 14:15:04
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Air-Filled Substrate Integrated Waveguide Fed Magneto-Electric Dipole Antenna Array for Millimeter-Wave Applications
摘要： A substrate integrated magneto-electric (ME) dipole antenna array with an improved radiation efficiency is presented in the 28-GHz band. A novel full-corporate air-filled substrate integrated waveguide (SIW) feed network with low losses is designed and realized by utilizing the low-cost printed circuit board (PCB) facilities. Different from most previous millimeter-wave planar arrays consisting of 2 × 2 sub-arrays, an SIW fed sub-array with a larger size of 2 × 4 is investigated to simplify the configuration of the major portion of the array feed network, which is of importance to the successful realization of the air-filled SIW feed network. An 8 × 8 array prototype with a four-layered geometry is fabricated and measured to verify the design. The array has an impedance bandwidth of 25.9%, a gain up to 26 dBi and stable radiation patterns over the operating band. Benefitted from the absence of the significant dielectric loss in the feed network, a high antenna efficiency of 80% is also achieved. The proposed design provides an effective method to improve the achievable gain and efficiency characteristics of the substrate-integrated arrays with a large size that are attractive for millimeter-wave wireless applications.
关键词： feed network,Antenna array,aperture-coupled magneto-electric (ME) dipole antenna,dielectric loss,millimeter-wave,air-filled substrate integrated waveguide (SIW)
更新于2025-09-11 14:15:04
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Sparse Scene Recovery for High-Resolution Automobile FMCW SAR via Scaled Compressed Sensing
摘要： This paper introduces a sparse scene reconstruction algorithm for automobile frequency-modulated continuous-wave synthetic aperture radar (FMCW SAR) through scaled compressed sensing (CS). An FMCW radar leads to low manufacturing cost, compact realization, and low transmission power. An automobile SAR is more economical and easier to implement than typical SAR platforms (e.g., satellites and aircraft). We apply CS to randomly subsampled raw data of automobile FMCW SAR for sparse reconstruction. We exploit the fact that the velocity of an automobile is significantly lower than that of the SAR platforms, which leads to a vastly narrow bandwidth of an azimuth-matched filter in the azimuth compression of the range-Doppler algorithm (RDA). Low-frequency azimuth data have a fundamental effect on azimuth compression. We propose a new reconstruction scheme, scaled CS, which specializes in low-frequency information recovery for automobile SAR. The scheme is based on basis pursuit denoising (BPDN). A Ku-band FMCW SAR system is developed to verify the performance of the proposed algorithm. We mount our system on an automobile and collect FMCW SAR raw data in the stripmap mode with a van maintained a constant speed on a highway. The proposed reconstruction algorithm shows improved recovery performance for automobile FMCW SAR, which is validated by processing a high-resolution real SAR image.
关键词： Automobile synthetic aperture radar (SAR),frequency-modulated continuous-wave (FMCW) radar,compressed sensing (CS),SAR,sparse reconstruction.
更新于2025-09-11 14:15:04
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Optical Properties of Bowtie-Type Nanoantennas Integrated Onto a Silicon Waveguide Platform
摘要： In this paper, we provide a detailed three-dimensional numerical analysis of the optical properties of common and modified bowtie aperture antennas integrated onto a silicon waveguide platform, to discuss the influence of geometrical parameters on the electric field enhancement factor and waveguide transmission when such antennas are excited by the evanescent field of the Si waveguide mode. We demonstrate that waveguide transmission is severely affected by the interference between Si waveguide modes and surface plasmon polariton modes excited in the antenna, while the antenna’s field enhancement factor is mainly determined by the localized surface plasmon resonance occurring in its nano-gap. These mechanisms lead to a mismatch between the wavelength at which the antenna’s field enhancement factor is maximized, and the wavelength at which transmission through the Si waveguide is minimized, suggesting that in some multi-mode cases, the optical properties of integrated nanoantennas determined through direct measurement of Si waveguide transmission may be misleading. Methods for improving the electric field enhancement (such that it has a bigger modulation depth) that have minimal impact on the resonant wavelength, and for improving the shape and location of the corresponding hot spot of the bowtie aperture antennas, are also discussed and analyzed. We believe that this analysis will be helpful in design of on-chip bowtie-type optical antennas for surface enhanced Raman spectroscopy, near-field optical microscopy, high sensitivity detection, and plasmonic optical tweezers.
关键词： Bowtie aperture antenna,Transmission,Silicon waveguide platform,Electric field enhancement
更新于2025-09-11 14:15:04
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High-resolution ISAR imaging of fast rotating targets based on pattern-coupled Bayesian strategy for multiple measurement vectors
摘要： Very high resolution inverse synthetic aperture radar (ISAR) imaging of fast rotating targets is a complicated task. There may be insufficient pulses or may introduce migration through range cells (MTRC) during the coherent processing interval (CPI) when we use the conventional range Doppler (RD) ISAR technique. With compressed sensing (CS) technique, we can achieve the high-resolution ISAR imaging of a target with limited number of pulses. Sparse representation based method can achieve the super resolution ISAR imaging of a target with a short CPI, during which the target rotates only a small angle and the range migration of the scatterers is small. However, traditional CS-based ISAR imaging method generally faced with the problem of basis mismatch, which may degrade the ISAR image. To achieve the high resolution ISAR imaging of fast rotating targets, this paper proposed a pattern-coupled sparse Bayesian learning method for multiple measurement vectors, i.e. the PC-MSBL algorithm. A multi-channel pattern-coupled hierarchical Gaussian prior is proposed to model the pattern dependencies among neighboring range cells and correct the MTRC problem. The expectation-maximization (EM) algorithm is used to infer the maximum a posterior (MAP) estimate of the hyperparameters. Simulation results validate the effectiveness and superiority of the proposed algorithm.
关键词： Multiple measurement vectors (MMV),Fast rotating target,Inverse synthetic aperture radar (ISAR),Migration through range cells (MTRC),Pattern-coupled hierarchical model
更新于2025-09-11 14:15:04
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Coherent Ray Tracing Simulation Of Non-Imaging Laser Beam Shaping With Multi-Aperture Elements
摘要： The application of laser light sources for illumination tasks like in mask aligner lithography relies on non-imaging optical systems with multi-aperture elements for beam shaping. When simulating such systems, the traditional approach is to separate the beam-shaping part (incoherent simulation) from dealing with coherence properties of the illuminating laser light source (diffraction theory with statistical treatment). We present an approach using Gaussian beam decomposition to include coherence simulation into ray tracing, combining these two parts, to get a complete picture in one simulation. We discuss source definition for such simulations, and verify our assumptions on a well-known system. We then apply our approach to an imaging beam shaping setup with microoptical multi-aperture elements. We compare the simulation to measurements of a similar beam-shaping setup with a 193 nm continuous-wave laser in a mask-aligner configuration.
关键词： Gaussian beam decomposition,laser beam shaping,mask aligner lithography,coherent ray tracing,multi-aperture elements
更新于2025-09-11 14:15:04
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Fiber Optic and Atmospheric Optical Communication || Dispersion Properties of Fiber Optic Structures
摘要： To understand dispersive properties of fiber optic structures that transmit optical continuous or pulse signals at long distances, propagating along such optical waveguides, different kinds of which have been discussed in Chapter 9, let us introduce, according to Refs. [1–7], several important engineering parameters that characterize the corresponding processes of optical communication via fiber links.
关键词： material dispersion,modal dispersion,dispersion,optical communication,numerical aperture,fiber optic structures
更新于2025-09-11 14:15:04
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Light absorption enhancement of plasmonic based photo-detector with double nanograting structure
摘要： This era of high speed photonic systems demands photo detectors to have large bandwidth, gain and improved light enhancement competence. Amongst the different light absorption enhancement methods being researched by the investigators, plasmonic has acquired increased attention in the last decades. Although single layer plasmonic supported metal semiconductor metal photo detector has been explored for higher light absorption efficiency, but exploration for double layer structure is lacking in literature. This paper presents performance of plasmonic based photodetector with double layer of nanogratings optimized at wavelength of 1.4 μm for night vision applications. Proposed design of plasmonic supported photodetector with double nanograting reports quenching factor of 92.14% and provides highest light enhancement with subwavelength aperture height of 60 nm. This can be credited to fact that both top and bottom layer of grating contributes to light trapping.
关键词： Surface plasmon polaritons (SPPs),Nanogratings,Nanomaterials,Plasmonics,Subwavelength aperture
更新于2025-09-11 14:15:04
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[IEEE 2019 International Topical Meeting on Microwave Photonics (MWP) - Ottawa, ON, Canada (2019.10.7-2019.10.10)] 2019 International Topical Meeting on Microwave Photonics (MWP) - Optimum Mitigation of distortion induced by Rayleigh Backscattering in Radio-over-Fiber links for the Square Kilometer Array Radio-Telescope
摘要： This paper presents theoretical and experimental study of unexpected distortions induced by the Rayleigh backscattering phenomenon in Radio-over-Fiber (RoF) links within the Square Kilometer Array (SKA) project. For this system, the radiofrequency (RF) signals coming from the sky and celestial sources are received by more than 130k antennas individually and then transmitted to the signal processing room through an analogue RoF link. The low frequency band considered (from 50MHz to 350MHz) and the relatively low levels of the power of such RF signals are identified as the cause of these distortion effects which can decrease drastically the receiver dynamic range. An analysis of the phenomenon is presented in this work, together with an efficient solution optimized for the considered applicative case.
关键词： Square Kilometer Array,Low Frequency Aperture Array,Radio-over-Fiber,Rayleigh Backscattering
更新于2025-09-11 14:15:04
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Machine Learning Framework for Mapping of Mississippi River Levees and Damage Assessment Using Terrasar-X Data
摘要： Earthen levees protect large areas of populated and cultivated land in the United States. Unstable slope conditions can lead to slump slides, which weaken the levees and increase the likelihood of failure during floods. Such slides could lead to further erosion and through seepage during high water events. Currently, levee inspections are performed infrequently and some of the problem areas are not visible. There is a need to develop cost-effective large-scale methods of screening levees in a timely manner. Sensing the condition of levees remotely can help levee managers to focus and prioritize their inspection and maintenance activities. This paper presents results of applying the TerraSAR-X synthetic aperture radar data to detect vulnerabilities on Francis, Mississippi river levees. In this study, texture features were computed using the discrete wavelet transform (DWT), and both supervised and unsupervised classifiers were tested. The supervised method tested is the SVM (support vector machine), and the unsupervised one is the RXD (Reed-Xiaoli Detector). Both algorithms achieved high accuracy detection of potential slump slides in the test area.
关键词： Levee classification,remote sensing,synthetic aperture radar (SAR),machine learning
更新于2025-09-11 14:15:04