基于参量下转换的单光子辐射基准源定标方法及应用研究

The traditional radiation technology is limited by the accumulation error of the transmission link and the problem of tracing to international SI unit. These factors made it difficult to meet the ten years climate change observation needs .The method of parameter down conversion which is an objective physical effect can be instead of a physical standard device. It is essentially self absolute "no traceable" calibration method. The correlated photons which can be be used to achieve all optical path calibration of a light radiation detector. will be produced by interaction between laser and nonlinear crystal. The wide tunable spectrum entangled photon theory ill be developed in this project. The effects of parameters such as gate width, dead time, after-pulse, delay, detection bandwidth and light source stability effecting on absolute accuracy will be analyzed. We will establish the maximum coincidence / coincidence rate and quantum efficiency correction model. We plan to prepare a wide dynamic range, high signal to noise ratio (SNR) and a high speed coincidence circuit based on TDC method..The key technologies of high accuracy measurement of optical system transmittance under weak light, development of a large dynamic range standard photon source, dead time,after-pulse and nonlinear measurement will be solved. This item will research optical radiation band range from 900nm to 1700nm and the calibration uncertainty will be obtained by 0.5%.It is expected to provide technical support for the establishment of the calibration system of the space radiation reference source in China.It lays the foundation for the quantification of remote sensing information

传统的辐射技术受限于传递链路累积误差和星上定标存在向国际单位SI的溯源的难题，难以满足10年尺度的气候变化观测应用需求。项目提出的参量下转换方法是以客观物理效应代替实物标准器，本质上是一种自身绝对的“无溯源”定标方法，利用激光与非线性晶体产生时间、空间、偏振、波长等相关的光子对，实现光辐射探测器的全光路无标准传递定标。解决参量下转换过程中的宽光谱可调谐光子源的制备，分析符合测量中的符合门宽、死时间、后脉冲，延时量、探测带宽和光源稳定性等参数对绝对精度的影响。建立最大符合/意外符合的比率和量子效率校正模型。研制基于TDC（时间数字符合测量法）的宽动态范围、高信噪比和高速符合电路。解决大动态范围标准光子源研制、死时间、后脉冲和非线性测量等关键技术问题。预计在900nm~1700nm范围内，量子效率测量精度达到0.5%。项目的开展有望为我国正在建立量子空间辐射基准源定标体系提供技术支撑。

自发参量下转换是采用“客观物理效应”替代实物标准器，理论上的具有更高的精度，符合国际单位制量子化趋势。本项目首先通过建立了完备的参量下转换定标物理模型，研究分析泵浦光中心波长，泵浦激光器线宽、相位匹配方式，晶体类型，泵浦光的光束质量、走离效应，晶体物理参数对参量下转换的影响。通过模型优化，获得了不同相位匹配方式的最佳聚焦条件，并分析不同聚焦条件下的光纤的耦合效率，为高通量相关光子源的制备提供理论基础。建立基于实测数据的光子数率与晶体温度关系模型，设计集晶体固定、温控为一体的集成晶体炉，测试了晶体的温度最发散角与转换效率的影响。设计激光聚焦模式下的光路对准方案和流程，实现激光聚焦模式下优于1mrad的光路光轴对准精度。开展了单色仪的光谱定标，建立了266nm/488nm的单色仪扫描宽光谱符合测量装置，获取了580nm/491nm、610/472nm、700/430nm、790/400nm、857\386nm、950nm\1003nm、780nm\1303nm七对相关光子的符合情况，它是目前国际上实现最宽谱段的相关光子连续符合测量结果。建立了488nm宽光谱符合测量装置，获取了950nm/1003nm、780nm/1303nm两对相关光子的通道量子效率。开展了PMT、SI APD与InGaAs APD的死时间与后脉冲测试。建立多参数的量子效率校正模型，评估基于相关光子的时间符合测量法的量子效率定标不确定度，分析了光子数率、符合带宽、符合与意外符合信噪比对符合测量精度的影响。通过与激光衰减法在633nm波段进行量子效率、死时间与后脉冲比对验证，确认测试精度。项目的开展有望为我国正在建立量子空间辐射基准源定标体系提供技术支撑。