We propose a novel method for object reconstruction of ghost imaging based on Pseudo-Inverse, where the original objects are reconstructed by computing the pseudo-inverse of the matrix constituted by the row vectors of each speckle field. We conduct reconstructions for binary images and gray-scale images. With equal number of measurements, our method presents a satisfying performance on enhancing Peak Signal to Noise Ratio (PSNR) and reducing computing time. Being compared with the other existing methods, its PSNR distinctly exceeds that of the traditional Ghost Imaging (GI) and Differential Ghost Imaging (DGI). In comparison with the Compressive-sensing Ghost Imaging (CGI), the computing time is substantially shortened, and in regard to PSNR our method exceeds CGI on grayscale images and performs as well as CGI visually on binary images. The influence of both the detection noise and the accuracy of measurement matrix on PSNR are also presented.

The silicon photonic optical phased array (OPA) featured by high integration and agile beam steering exhibits greatly potential application in optical wireless communication (OWC). In this paper, we demonstrate high-data-rate and long-range OWC using an integrated Silicon-Silicon Nitride OPA chip with 12 mm ² large aperture. The OPA chip constituted by 128 waveguide grating antennas at nonuniform spacing is employed for wide-steering and small-divergence solid beam steering. In the experiment, we demonstrated 100° wide range communications in horizontal direction via antenna phase tuning. To our best knowledge, 100° is the widest cover range in the reported OPA-based OWC systems. Moreover, the OPA chip is also utilized to achieve up to 32 Gb/s low BER transmission of non-return-to-zero (NRZ) signal over 54 m free space distance. In addition, we also successfully demonstrated more than 50 Gb/s PAM4 signal transmission by measuring clear eye diagrams at the horizontal direction of 0° and 50° over 10 m. Thanks to agile beam steering of the OPA, switching time among arbitrary positions in multi-targets communication can be less than 27 μs. By virtue of tiny beam divergence 0.021° × 0.029° emitted from the OPA, data transmission switching between two targets spaced at 3.5 cm over 20 m can be achieved accurately. The experimental measurement shows the sidelobe crosstalk from the adjacent target channel is less than -25.2 dB. Our demonstrations validate the feasible implementation of the silicon-based OPA in the high-data-rate and wide-steering-range OWC system.

The features of the characteristic matrix used in linear intensity correlation reconstruction methods are directly related to the quality of ghost imaging. In order to suppress the noise caused by the off-diagonal elements in the characteristic matrix, we propose a reconstruction method for ghost imaging called scalar-matrix-structured ghost imaging (SMGI). The characteristic matrix is made to approximate a scalar matrix by modifying the measurement matrix. Experimental results show that SMGI improves the peak signal-to-noise ratio of the object reconstruction significantly compared with differential ghost imaging, even in the case of a nonzero two-arm longitudinal difference, which is a promising result for practical applications.

We propose a method that realizes laser ranging and communication at the same time based on dual-pulse interval modulation (DPIM). The transmission of binary data bits in the communication process is realized by sending two laser pulses continuously, and the time interval between the dual pulse is used to characterize the value of this bit (0 or 1). Meanwhile, the echo signal received by the communication transmitter is also a dual pulse signal, which enables laser ranging by the time-of-flight (TOF) principle. This method can effectively improve the reliability of system communication. Furthermore, the system structure is rather simple, including one piece of field programable logic gate array (FPGA) chip, one piece of time-to-digital converter (TDC) chip, and a transmitting and receiving circuits. The experimental results show that this method and system can achieve effective and reliable transmission of 2-D images and characters at the ranging accuracy of a single laser ranging system.

The optical phased array (OPA) chip is becoming the core component of all-solid-state lidars. In order to realize the wide-angle range beam scanning and rapid control of OPA-based solid-state lidars, we design and fabricate a 64-channel silicon-based OPA chip based on thermo-optical modulation. In accordance with the optical phase control characteristics of the multichannel thermo-optic OPA chip, we propose a parallel random access memory (RAM) array technique to realize high-speed phase control for the OPA chip and build the hardware system with a field-programmable logic gate array (FPGA). This system is used to test the main performance indicators of the OPA chip and realizes the high-speed scanning control of the wide-angle range of the OPA output beam. The test results show that the OPA chip we designed can achieve fast beam scanning within a large angle range between −32.5° and +32.5°, and the chip has high working reliability. Combined with the control system we build, it can meet the high-speed radar scanning requirements of all-solid-state lidars. This work lays a good foundation for the subsequential development of our thermo-optical and electrooptic OPA all-solid-state lidar prototypes.

In this letter, we report a cascaded surface-illuminated Germanium-on-Silicon (Ge-on-Si) avalanche photodiode (APD) array with a low dark current. The photodetector array cascades seven Ge-on-Si APDs through interconnecting the charge regions to form photomultiplier tubesiPMTjC which increases the effective light absorption area compared to the single APD scheme. To the best of our knowledge, this is the first time that Ge-on-Si PMT has been reported. The optimum response of single-electrode (2 pixels) Ge-on-Si APD is 2.4 A/W with a dark current of 100 nA, and the optimum bandwidth is 52 MHz. PMT has a responsivity of approximately 3 times that of a single-electrode Ge-on-Si APD for the same dark current (100 nA). With low dark current, our PMT has a better optical amplification effect than the parallel Ge-on-Si PD. We have also further tested the current tuning properties of the Ge-on-Si APD arrays with different applied Ge voltages. The test demonstrates the feasibility of cascading three-electrode APD arrays. A cascaded Ge-on-Si APD array with good photodetection properties at low-light conditions has been demonstrated which provides guidance for the design of large-scale Ge-on-Si APD arrays for light detection and ranging application.