宽谱高效率、偏振不敏感的超导纳米线单光子探测器

Superconducting-nanowire single-photon detectors have attracted tremendous research interest and have been applied to applications including quantum communications and measurements, ultra-long haul optical communications, due to their high efficiency, low dark count rate, short reset time, and low timing jitter in the near-infrared spectrum. However, two important properties have not yet been realized on one single detector of this type: first, high-efficiency in broadband; second, polarization insensitiveness. The difficulties to realize these two properties on the same device are that, firstly, the field is lack of systematic, quantitative studies of the internal efficiency and, secondly, as far as the traditional meander structure is concerned, these properties require structural parameters that are tradeoffs. This project will use ultra-narrow superconducting nanowires integrated with waveguides on chip to simultaneously realize high-efficiency in broadband and polarization insensitiveness, will use this structure of waveguide-integrated nanowires to quantitatively and systematically study the internal efficiency, in particular, the dependence of internal efficiency on the wavelength, polarization, and the width of the nanowire, and will feedback the study of the internal efficiency to the design of the detectors. Broadband efficient, polarization-insensitive superconducting-nanowire single-photon detectors would benefit the characterization of broadband entanglement generated by frequency comb and polarization entanglement.

超导纳米线单光子探测器因为在近红外波段具有探测效率高、暗计数低、响应恢复时间短、时域抖动小等卓越性能，成为单光子探测领域的研究热点，并逐渐被应用于量子通信与测量、超长跨距光通信等领域。然而，有两点重要的性能尚未在此种探测器的同一器件上实现：第一，宽谱范围高效率；第二，偏振不敏感。同时实现这两点性能的难点在于：第一，本研究领域对此类探测器的内效率缺乏定量的系统研究；第二，对于传统基于回型线结构的器件而言，这两点特性对器件结构参数的要求是矛盾的。本研究项目拟采用与波导在芯片上集成的超细超导纳米线，同时实现宽谱高效率和偏振不敏感这两点性能；且利用波导集成的探测器结构，定量地、系统地研究内效率，尤其是研究、测量内效率与光波长、偏振态、纳米线宽度之间的关系，并以此为依据进一步优化设计探测器结构。宽谱高效率、偏振不敏感的单光子探测器将对频率梳产生的宽谱纠缠态、偏振纠缠态的表征有所助益。

超导纳米线单光子探测器(SNSPD)成为近年来的研究热点。本项目围绕SNSPD领域有待解决的关键科学技术问题——宽谱高效率偏振不敏感的SNSPD器件——展开研究工作，并取得如下研究成果：第一，设计并实现了对任何偏振态的入射光子探测效率都高于60%、偏振敏感度低于1.05的SNSPD器件；第二，从理论和实验两个方面较为系统地研究了SNSPD的内量子效率和时域性能。这些研究工作为进一步提升SNSPD的性能，拓展SNSPD的应用空间有帮助。在本项目的支持下，在Applied Physics Letters、Optics Letters等学术期刊上发表研究论文4篇，在CLEO等学术会议上发表研究论文7篇，获批发明专利2项，在国际学术会议上做邀请报告5次，培养博士研究生1名、硕士研究生4名。