光学谐振腔不仅可以增强激光和物质的相互作用，而且能够抑制激光的噪声，是开展精密测量、量子光学等研究的重要工具。激光和光学谐振腔共振的稳定锁定是其应用的关键。然而，在实际环境中锁定效果会受机械振动、温度变化等因素的影响。提出了将模糊算法应用于PDH （Pound-Drever-Hall）技术，使比例积分微分控制器的三个参数能够根据外界环境变化进行调节以实时获得最优参数，有效提升了光学谐振腔的锁定的抗干扰能力。如果外界干扰仍然过大以至于失锁，系统可以使其自动重新锁定。该系统有效增强了光学谐振腔的实用性，为光学谐振腔在精密测量、量子光学实验中的应用提供了技术基础。

The intensity difference squeezed state, which means that the fluctuation of the intensity difference between signal and idler beams is less than that of the corresponding shot noise level (SNL), plays an important role in high sensitivity measurement, quantum imaging, and quantum random numbers generation. When an optical parametric oscillator consisting of a type-II phase-matching periodically poled KTiOPO4 crystal operates above the threshold, an intensity difference squeezed state at a telecommunication wavelength can be obtained. The squeezing of 7.7±0.5 dB below the SNL is achieved in an analysis frequency region of 2.4–5.0 MHz.

A low-noise photodetector is a basic tool for the research of quantum information processing. We present a specially designed low-noise photoelectric detector with a bandwidth of 130 MHz, using a transimpedance amplification circuit. Based on the detailed calculation of the dependence on each parameter of the detector, a useful method of how to design a low-noise and broadband photodetector is provided. When the optical power is between 1.0 and 16 mW, the photodetector has a good linear response to the injected light. Its electronics noise power is below 77 dBm, which is within the whole bandwidth. When the incident light power is 2 mW, the output noise powers are 10.0, 8.0, and 6.0 dB higher than the corresponding electronics noise within the bandwidth of 1–50, 50–90, and 90–130 MHz, respectively, which is in good agreement with the theoretical prediction. Thus, this photoelectric detector could have good application prospects in quantum communication and an optical cavity locking system.