为了实现对光泵原子磁力仪系统中发散的快速调制光信号的精密相位检测，解决现有平衡光电探测器存在的接光面积小、增益小、带宽小及相位性能不理想等问题，本文采用基于结点差分电流的平衡差分探测方法，分析了平衡探测器抑制系统共模噪声的机理，通过优化元件和提高带宽设计出具有低相位噪声且单管接光面尺寸达到10 mm的大面积平衡光电探测器，并进一步利用双板隔离式的制作方法避免了热噪声干扰，实现了其低相位漂移的特性。实验结果表明，该探测器-3 dB带宽达到1.1 MHz，信号跨阻增益达到0.91 MΩ，在175 kHz调制光信号下的相位噪声峰峰值不超过0.002 3°，能够满足碱金属原子磁力仪系统光信号精密相位检测的要求。

In order to achieve accurate phase detection of diverging and rapidly modulated light signals in optically pumped atom magnetometer systems and to solve the problems of existing commercial balance photodetectors in terms of small optical sensitive area, small gain, small bandwidth, and poor phase performance, the balanced differential detection method based on Kirchhoff's law is adopted in this paper. The mechanism for system common mode noise suppression is analyzed and a low phase noise balanced amplified photodetector, the sensitive area size of which reaches 10 mm per photodiode, is designed. Moreover, a two-board-isolation fabrication method is applied to avoid thermal noise and a low phase drift characteristic is achieved. Experimental results show that the -3 dB bandwidth of the photodetector reaches 1.1 MHz, with a signal transimpedance gain of 0.91 MΩ, while the peak-to-peak phase noise at 175 kHz modulated optical signal does not exceed 0.002 3°. The photodetector meets the requirements of optical signal precision phase demodulation in alkali metal atom magnetometer systems.