Quantum ghost imaging based on a "looking back" 2D SPAD array

A comparison between the measurement of quantum spatial correlations using qCMOS photon-number resolving and electron multiplying CCD camera technologies

Cameras with single-photon sensitivities can be used to measure the spatial correlations between the photon-pairs that are produced by parametric down-conversion. Even when pumped by a single-mode laser, the signal and idler photons are typically distributed over several thousand spatial modes yet strongly correlated with each other in their position and anti-correlated in their transverse momentum. These spatial correlations enable applications in imaging, sensing, communication, and optical processing. Here we show that, using a photon-number resolving camera, spatial correlations can be observed after only a few 10s of seconds of measurement time, thereby demonstrating comparable performance with previous single photon sensitive camera technologies but with the additional capability to resolve photon-number. Consequently, these photon-number resolving technologies are likely to find wide use in quantum, low-light, imaging systems.

Real-time ghost imaging algorithm on the multidimensional vector matrix Walsh transformation with spatiotemporal free-fps

In this research, we propose a real-time spatiotemporal free-fps algorithm based on the multidimensional vector matrix Walsh transform with an adjustable ghost imaging video quality and a frame rate to address the issues of uneven imaging speed, fixed imaging frame rate, and uncomfortable appearance in real-time ghost imaging videos of moving objects. This algorithm utilizes the temporal and spatial correlation of ghost imaging videos to achieve free and adjustable video frame rates in time without being limited by DMD refresh rates. Improving the spatial information of a single frame in space enhances the smoothness of ghost imaging videos, making the appearance of ghost imaging videos more comfortable. To achieve this, a four-dimensional vector Walsh transform kernel matrix is used to transform and reconstruct the high-quality images of the target object. Then the reconstructed high-quality image is spatially interpolated to enhance spatial information. Reasonable frame rate parameters are set based on the corresponding relationship between the detection values of the adjacent frames and speckle, improving the ghost imaging video in both time and space and achieving a smooth real-time ghost imaging video with an adjustable quality and frame rate. The simulation and experimental results of moving objects show that our algorithm solves the limitation of a DMD refresh rate compared with the existing ghost imaging video methods and makes the ghost imaging video more comfortable and smoother in real time. The PSNR of the objective evaluation index is increased by 12%. Regarding a subjective evaluation, this paper proposes an adaptive parameterless evaluation algorithm (APEA) for images with different resolutions based on the NRSS, which improved the structure retention degree by 13% and the Brisque parameter evaluation by 70%. We propose an adaptive parameterless video comfort evaluation algorithm (APVCEA) to evaluate the subjective comfort of ghost imaging videos by 14% compared with traditional methods.

Design and simulation of a near-infrared enhanced Si-based SPAD for an automotive LiDAR

A near-infrared (NIR)-enhanced single-photon avalanche diode (SPAD) with a retrograded NM/XP junction for an automotive LiDAR was designed based on CSMC 0.18 µm BCD technology. A 3 µm depth NM/XP junction embedded in a lightly doped deep p-well (DP) improves the absorption efficiency in the NIR regime; the photo-generated electrons generated in the depletion region are efficiently collected into the central multiplication region by a drift process, and then the impact ionization is triggered by the strong field, resulting in a high photon detection efficiency (PDE). Additionally, the deep NM/XP junction and the buried layer effectively isolate the dark noise originating from the interface and the substrate. The SPAD was initially simulated by numerical calculation, and then was evaluated with active quench/reset electronics in a circuit simulator. The results revealed that the SPAD with an active area of 314µm 2 achieves a PDE of 16.2% at 905 nm and a dark count rate (DCR) of 1.46H z/µm 2, with an excess bias of 5 V at room temperature. The designed SPAD is well suited for the low-cost, miniaturized automotive LiDAR.