Philippe L C, Hanson R K
Appl Opt. 1993 Oct 20;32(30):6090-103. doi: 10.1364/AO.32.006090.
Wavelength modulation at 10 MHz of an AlGaAs laser diode, superposed on repetitive linear scans of wavelength, is applied to measure second-harmonic absorption line shapes of oxygen in the A band. Theoretical expressions of the harmonic line shapes, including the effect of laser amplitude modulation and varying modulation depth, are presented. A least-squares fit of the experimental line shapes to theoretical second-harmonic line shapes permits simultaneous determination of the temperature and the pressure. The use of high-repetition-rate (10-kHz) linear scans of the studied wavelength region permits application of the technique to high-speed unidimensional transient flows generated in a shock tube; velocity is derived from the Doppler shift of the absorption profiles.
将一个铝镓砷激光二极管在10兆赫兹下的波长调制叠加在波长的重复线性扫描上，用于测量A波段中氧气的二次谐波吸收线形。给出了谐波线形的理论表达式，包括激光振幅调制和调制深度变化的影响。将实验线形与理论二次谐波线形进行最小二乘拟合，可以同时测定温度和压力。在所研究的波长区域使用高重复率（10千赫兹）的线性扫描，使得该技术能够应用于激波管中产生的高速一维瞬态流；速度由吸收谱线的多普勒频移得出。
