激光偏振特性对可调谐半导体激光吸收光谱测量技术的影响研究

Effects of Laser Polarization Characteristics on Tunable Diode Laser Absorption Spectroscopy

关键词:  可调谐半导体激光吸收光谱  偏振态  流场参数测量  光纤光学

Key words:  TDLAS  Optical polarization  Flow field measurement  Fiber optic

摘要:

为了解决TDLAS系统在工程应用中对发动机或激波管内流场测量时所遇到的偏振干扰问题，开展了传输激光偏振特性对TDLAS测量技术的影响研究。基于一个典型TDLAS工程应用系统的传播光路，推导了TDLAS工程测量系统中归一化出射光强随入射光波偏振角的变化关系式，利用这个关系式从理论上研究了由于入射光波偏振态扰动而引入的偏振噪声，利用实际工程测量中使用的发动机尾喷管搭建了实验验证系统，并通过实验对理论分析进行了验证，结果证明通过正入射方式或采用保偏光纤可以将幅度抖动范围在20%以上的偏正扰动有效地消除，根据理论分析和实验结果提出了抑制这种偏振噪声的具体实施方案。

Abstract:

Aiming at the problems of polarization interference of TDLAS system which were encountered in measuring the physical parameters of the flow field in the engines or shock wave tubes，the research was carried out on the effects of the polarization characteristics of the optical light on TDLAS measurement technology. A formula of relationship between the normalized output intensity and the change of polarization angle of optical light was deduced based on a typical optical path model in practical TDLAS application system. According to this formula of relationship，the polarization noise induced by the fluctuation in the polarization state of optical signal was analyzed in theory. With an engine nozzle used in practical measurement system，an experimental verification system was set up to validate the theory analysis. The results show that the intensity jitter whose range was more than 20% could be effectively eliminated by the positive incident mode or by using the polarization maintaining fiber. And several specific implementation methods were put forward based on the theoretical analysis and experimental results to suppress the polarization noise.