外腔式二极管激光器的低频电压波长调制和谐波探测的实验研究

Experimental Study of Low-frequency Voltage Wavelength Modulation and Harmonic Detection Using an External-cavity Diode Laser

对单模、可调谐外腔式二极管激光器采用调节激光外腔压电电压的方法实现波长调制 ,利用数字锁相放大器处理光谱信号的高次谐波。通过对 Cs原子 D2 线的谐波探测证明用高于二次的高次谐波探测气体的直接吸收光谱可以获得更高的分辨率和信噪比。

A low frequency wavelength modulation spectroscopy is acquired with an external cavity tunable diode laser. The wavelength modulation is achieved using the voltage tuning by scanning the piezoelectric stepper motor with rotating of the end mirror in the laser cavity. With optimum modulation frequency of 1 kHz a harmonic detection processed by a lock in amplifier for cesium D 2 line was carried out. It is found that 6f harmonic detection is best here with the signal to noise voltage ratio (SNR) being 460. It is also shown that nearly overlapping lines may be better resolved by using 6f harmonic detection due to the much less modulation broadened spectra.