中红外激光光源覆盖了大量气体的基频吸收带,尤其适合于痕量气体的高灵敏检测。其中具有高输出功率、宽调谐范围、能够在室温工作的量子级联激光器为高灵敏痕量气体检测技术的研究提供了理想的光源。基于脉冲量子级联激光器的脉内光谱技术提供了一种简单而又有效的测量痕量气体的方法。当一个长激发脉冲作用在激光器上时,激光器的频率随着脉冲持续时间的增加而线性减小,从而在单个脉冲上扫描出被测气体分子的特征吸收谱线,实现对目标气体的定性或者定量分析。介绍了基于分布式量子级联激光器的脉内光谱技术,并采用该技术对N₂O 进行了光谱测量。一个500ns的长激发脉冲应用在脉冲量子级联激光器上用于快速波长扫描,达到接近1cm^-1的线性调谐范围,得到了中心在1274cm^-1附近的N₂O的吸收谱线,与HITRAN数据库相应的N₂O 吸收谱线有着良好的一致性。

Mid-infrared lasers are very suitable for high-sensitive trace-gases detection in that their wavelengths cover the fundamental absorption lines of most gases. Quantum-cascade lasers have been demonstrated to be ideal light sources with their especially high power, wide range of tuning capability and favorable operating condition on roomtemperature. The intra-pulse spectroscopy based on a room-temperature distributed-feedback pulsed QC laser is a simple and effective trace gas detective method to detect trace-gas qualitatively or quantificationally. When a long excitation pulse is applied to a QC laser, the laser frequency tunes almost linearly to lower wave number(lower frequency) as a function of time so all absorption spectral elements are recorded during a single laser pulse. In the present paper, the method was introduced, and identification of N₂O spectral fingerprint using this spectroscopy was demonstrated experimentally. The thermal chirp from a 500 ns long excitation pulse was applied to a quantum-cascade laser to get a fast wavelength scanning, thus a wave number tuning of about 1 cm^-1 was produced. The N₂O absorption spectrum centered at 1273.7cm^-1 was also obtained. The measured absorption spectrum is consistent with HITRAN data precisely.