为实现中红外波段的高精度线型研究, 建立了一套在2.5～5 μm波段连续可调谐的中红外差频激光光谱测量系统。基于宽带连续可调谐钛宝石激光器(700～900 nm)和单频连续Nd:YAG激光器(1064 nm), 利用碘多普勒展宽吸收和频率调制技术, 对Nd:YAG激光的频率进行反馈控制, 使1064 nm的Nd:YAG激光的波长稳定性好于1×10-5 cm-1。由此差频输出的波长稳定性达到1×10-4 cm-1水平, 适合高精度的线形研究。并通过对CH4分子在2927 cm-1附近吸收谱线的测量, 表明该系统可以结合频率调制方法, 进行高灵敏的光谱检测。

To study the precise line profile in the mid-infrared (MIR) region, a versatile continuous wave (CW) MIR difference frequency generation (DFG) spectrometer is built up utilizing a CW Ti:Sapphire laser (700～900 nm) and a CW single-frequency 1064 nm Nd:YAG laser. The spectrometer covers the 2.5～5 μm region by tuning the frequency of the Ti:Sapphire laser. The frequency of the Nd:YAG laser is stabilized within 1×10-5 cm-1 when it is locked on the Doppler-broadened I2 absorption line near 532nm. As a result, the DFG laser frequency is stabilized to the level of 1×10-4 cm-1, which is suitable for precise line profile measurements. An absorption line of CH4 near 2927 cm-1 was recorded using this spectrometer and it presents an example for the sensitive detection with the frequency-modulation spectroscopy method.