高速平衡零拍探测器的设计与实现

Design and implementation of high-speed balanced homodyne detector

平衡零拍探测器存在共模抑制比小、响应带宽低等问题。针对以上问题,尝试从两方面进行改进:一方面,通过测试探测器中光电检测器(PIN光电二极管)的响应特性,选择性能相近的器件进行平衡探测,以提升共模抑制比;另一方面,采用跨阻放大与比例运放级联的方式对光电流信号进行提取,解决一级采样放大器增益带宽积局限的问题,在保障灵敏度的同时提升探测器的响应带宽。由此实现了300 MHz的平衡零拍探测,共模抑制比高达66 dB,并有效检测了光信号中的量子散粒噪声,为高速灵敏探测提供了一种有效技术方案。

Balanced homodyne detectors have the disadvantages such as small common mode rejection ratio(CMRR)and low response bandwidth,etc.To address the problems,we designed a scheme to test the response characteristics of the photodetector(PIN photodiode)in the detector and selected devices with similar performance for balanced detection to improve the CMRR.Furthermore,the scheme of cascading transimpedance amplification and proportional operational amplifier were proposed to extract the photocurrent signal,which solved the problem of the limitation of the gain bandwidth product of the primary sampling amplifier and improved the response bandwidth of the detector while ensuring the sensitivity.As a result,we achieved 300-MHz balanced homodyne detection and the CMRR went up to 66 dB.We also detected the quantum shot noise in the optical signal.These achievements provide an effective technical scheme for high-speed sensitive detection.