激光稳频控制系统仿真与实验研究

Simulation and Experimental Studies on Laser Frequency Stabilization Control System

摘要:

窄线宽稳频半导体激光器在干涉测量、光学频标、精密光谱测量等研究领域有着广泛的应用。自由运转的半导体激光器每天的频率漂移量可以达到GHz,因此研究半导体激光器的稳频具有十分重要的意义。本文以PDH稳频为例,基于PLL理论建立了激光稳频过程的数学模型,计算了激光稳频过程的误差传递函数。利用Matlab/Simulink搭建了激光稳频仿真模型,分析了环境变化时激光器失锁机理,结果表明控制电路内部信号可作为失锁判据。进一步利用积分扫描方式搭建了一套激光器稳频试验系统,针对环境因素的变化,对激光器失锁过程进行了研究,实验结果与仿真结果基本一致。同时在稳频系统精密控温的情况下,实现了对激光器长时间稳频,其频率不稳定度小于5MHz。

Abstract:

Semiconductor laser with narrow linewidth and high frequency stability has been widely used in interference measurements, optical frequency standard and precision spectroscopy. The daily frequency drift of a free running semiconductor laser can reach GHz level. Therefore, it is very important to study the frequency stabilization of semiconductor laser. In this paper, a mathematical model of laser frequency stabilization control system based on the phase locked loop (PLL) theory is proposed. The principle of lock-lose is been analysed and simulated by employing Matlab/Simulink. The result shows that the internal signal of the control circuit can be applied as the criterion of the lockout. Furthermore, an experimental phase-locking system is built with the integral scanning method to measure the actual locking performance. The good agreement of the results between the experiment and simulation presents that the theoretical model is reliable. Under the condition of precise temperature control, the laser shows excellent long-term frequency stabilities with a instability frequency below 5MHz.