Balanced Homodyne Detector Based on Two-Stage Amplification

Abstract

With the characteristics of high sensitivity and low noise, balanced homodyne detection technique has been one of the main methods in quantum noise measurement. Based on the Kirchhoff's law, a balanced homodyne photoelectric detector with two-stage amplification is designed and studied. The differential photocurrent of two similar photodiodes is primarily amplified by a trans-impedance amplifier, and then sent into the secondary differential amplifier. Experimental results show that the saturation power of this detector is 5 mW, and the signal response bandwidth is about 140 MHz. When the input laser power is equal to 2 mW and the frequency is lower than 30 MHz, the optical shot noise is 10 dB larger than the electronic noise. Near 20 MHz, the common mode rejection ratio of the detector could reach 55 dB.

Locking of Optical Transfer Cavity Based on PDH Technique

“…低温度约 2 mK。实验中冷却激光为染料激光器， 冷却激光波长为 614 nm。再抽运激光为 648 nm 和 649 nm， 都为半导体激光器。实验中将这些激光锁定到拍频的掺铒光纤光梳上 [6] 。华东师范大学印建平小组也在开 Fig.2 Measurement results of free spectral range of F-P cavity 实 验 上 ， 采 用 激 光 相 位 调 制 法 来 测 定 F-P 腔 的 精 细 度 [12] 。 采 用 了 一 个 谐 振 频 率 为 20 MHz 的 电 光 相 位 调制器对入射光进行相位调制， 并以三角波驱动 PZT 进行线性扫描， 并利用光电探测器探测透射光， 获得了 F-P 腔的共振透射谱线。F-P 腔的基本参数如表 1 所示。 [13] ； C3 为 经混频、 低通滤波后， 得出的鉴频曲线。由于色散信号在中心共振频率处幅值为 0 且为奇对称， 斜率也很大， 因此适于做鉴频信号。 图 3 实验测得的 780 nm 光与 F-P 腔作用的色散型误差谱线 Fig.3 Measured dispersion error of interaction of laser with 780 nm wavelength and F-P optical cavity 在获得色散型误差信号后， 就可以进行 F-P 腔的锁定。首先， 逐渐减小 F-P 腔的扫描电压， 并调整 PZT…”