基于超导纳米线单光子探测器的1.5 μm波长强度关联成像研究

Superconducting nanowire single-photon detector (SNSPD) has many outstanding performances in single photon detecting, such as a wide spectral response range, a high quantum efficiency, a low dark count rate, and a high timing resolution, as well as a high count rate. SNSPD has a better comprehensive performance than conventional semiconducting single-photon detectors at the near-infrared wavelengths, and became a mainstream used in these wavelengths. The application of SNSPD in intensity correlated imaging with pseudo-thermal light will widen the application wavelength of the imaging system to 1.5 μm and may advance the practical course of this technology. We will carry out intensity correlated imaging lidar based on SNSPD technology at the wavelength of 1.5 μm, and fabricate SNSPDs with high performance for 1.5 μm wavelength with large photosensitive-area, high detection efficiency, as well as fast operating speed. By clarifying the influence of the SNSPD parameters on the imaging quality, we may improve the stability and applicability of the SNSPD for imaging applications. And the advantages and disadvantages of applying the near-infrared wavelength in intensity correlated imaging will be analyzed as well. This project may also lay a good foundation for the research of long range intensity correlated imaging at near-infrared wavelengths in complex environments.

超导纳米线单光子探测器（SNSPD）作为一种新型的探测器，具有响应光谱宽、量子效率高、暗计数率低、时间精度高、计数率高等优势，在近红外波段其综合性能明显超越传统的半导体单光子探测器，成为主流探测器之一。将近红外高性能SNSPD应用到基于赝热光源的强度关联成像中，有望将强度关联成像从传统的可见光波段拓展到近红外波段，进一步提升强度关联成像的应用范围。本项目拟基于SNSPD开展1.5 μm波长强度关联成像研究，掌握针对成像应用的大光敏面SNSPD单元器件制备的关键工艺，研制出大光敏面、高探测效率、高速率的SNSPD器件，搭建1.5 μm波长强度关联成像实验装置，通过成像实验研究阐明近红外波段强度关联成像对单光子探测器的需求以及其性能和器件参数的关联，分析近红外工作波长强度关联成像（和可见光波长相比）的优缺点。该研究将为近红外波段、远距离、复杂环境下的强度关联成像研究奠定一定的基础。

强度关联成像(Intensity correlated imaging)是一种利用热光场辐照目标,由一个无空间分辨能力的单像元探测器获取目标返回信号的涨落信息,通过涨落信息与探测热光场之间的二阶关联运算获取目标图像信息的非局域成像方法。本研究首次利用SNSPD进行了1.5 μm波段的强度关联成像研究，最终成像分辨率达到2 mm，物方大小可达25mm*25mm，对应像素数55*55，相应的极限分辨率为36 μm*36 μm。其中制备的1.5 μm波段的50 μm芯径多模光纤耦合的大光敏面SNSPD 除了可以用于强度关联成像的研究，还可用于远距离红外激光成像，激光测距以及荧光探测等领域。目前制约成像效果的主要因素为单光子探测器的动态范围不够。为了提升强度关联成像的成像效果，提升SNSPD的动态范围，我们初步研制了光敏面直径为300μm，9像素的SNSPD，其在1.06μm的探测效率可达42%。通过此项目研究，我们掌握了大光敏面SNSPD器件制备的关键技术，制备的大光敏面器件同时可用于高速激光通信、激光雷达等领域。在后续研究过程中，我们会将超大光敏面器件的制备研究推进到1.5 μm波段，并将其应用在强度关联成像系统中，预计会获得较好的结果。