室温工作的连续可调谐相干光源在痕量气体检测技术中有着重要的应用价值，非线性差频方法是获得室温工作的中红外相干光源的有效途径，是对传统激光光源的重要补充。报道了一种基于差频方法的室温工作宽调谐中红外激光光谱系统，使用两台近红外半导体激光器作为种子光源，采用PPLN晶体作为非线性混频器件，结合准相位匹配技术实现了3．2～3．7 μm中红外相干光源输出，最大差频输出功率约为1 μW。对CH4基频吸收谱线的光谱检测表明，系统能够满足在中红外光谱区对气体成分进行高分辨、高灵敏、快速吸收检测的需要。

The availability of room-temperature continuous-wave tunable narrow band coherent light sources emitting in the mid-infrared region is greatly valuable for trace gas sensing techniques. Nonlinear optical difference-frequency generation(DFG)scheme was a useful way to meet the requirement and good complementarities for traditional laser technology. A widely tunable room-temperature mid-infrared spectrometer was reported and the instrument was based on the quasi-phase-matched DFG of two near-infrared diode lasers in multigrating periodically poled LiNbO₃ crystal. The mid-infrared coherent radiation was produced from 3.2 to 3.7 μm with a maximum output power of about 1 μW. The generated mid-infrared coherent radiation was applied to high-resolution detection of CH₄ in the fundamental band,which showed the great promising of the instrument used in sensitive,high-resolution and fast response measurements of trace gas in the mid-infrared region.