根据光电二极管的等效电路图,基于自减方案的平衡零拍探测器的光电管(ETX500)产生的光电流的位相差异主要由等效电容引起, 通过给两个光电管施加不同的偏置电来补偿等效电容的差异获得高共模抑制比的平衡零拍探测器,在探测器中安装任意两个ETX500,获得了638 dB的高共模抑制比,并且当激光功率达到探测器的饱和功率54 mW时,激光光场的噪声谱在2 MHz处高于电子学噪声37 dB,该探测器能很好地满足压缩态探测对低噪声、线性增益及高共模抑制比的要求。

Based on the self-subtraction photodetector scheme, The phase difference is induced from the discrepancy of the equivalent capacitance of two photodiodes.According to the design of the adjustable bias voltage circuit, we adjusted the bias voltage of two photodiodes and made it equal. As a result, a balanced homodyne detector, with the maximum common mode rejection ratio and clearance of 638 dB and 37 dB,was experimentally obtained with two arbitrary photodiodes with the same model, with the clearance of 37 dB at input power of 54 mW. The photodetector is an important tool of detecting squeezed light.