A new method of absolute calibration of photodetector sensitivity based on spontaneous parametric down - conversion ( spdc ) biphoton field is described . the process of spdc is studied theoretically . the single photon detection probability and two - photon coincidence probability are derived and the calibration principle for photodetectors is explained . an experimental system has been set up . the sensitivity of a photon - counting photomultiplier tube was measured , and the results were compared with those obtained using conventional method 讨论了一种基于自发参量下转换双光子场绝对校准光电探测器灵敏度的新方法，着重推导了对自发参量下转换过程中产生的单光子的探测概率和双光子的符合速率，从而阐明了绝对测量光电探测器量子效率的原理.基于这一方法对光子计数型光电倍增管的响应灵敏度进行了测量，并将实验结果与常规方法测得的结果进行了比较
In the field of fundamental research , such as quantum optics , blue light can be used as a pump source of optical parametric oscillator ( opo ) to generate the neoclassical light fields around wavelength of 860nm , which can be detected with 99 . 9 % of quantum efficiency , the highest efficiency in the measurement of neoclassical light as known yet it is also possible to generate the squeezed vacuum state at 852nm , which is the resonance wavelength of the transition line d2 of cesium atoms and can be supposed to investigate the properties of atomic radiation in the interaction between atoms and quantum state of light fields 在量子光学中，该蓝光作为下转换的泵浦源，可以产生860nm非经典光场，其探测效率可达99 . 9 ，高于目前产生的其他任何波段的非经典光场。同时通过温度调谐，可望产生与铯原子d2线作用的852nm波段的压缩真空态，从而开展非经典光场与冷原子的相互作用等方面的实验研究。本文主要通过knbo _ 3晶体外腔谐振倍频技术来产生蓝色激光光源。
