基于QCL的红外吸收光谱技术的研究进展

Progress of Measurement of Infrared Absorption Spectroscopy Based on QCL

量子级联激光器作为一种新型的单极型半导体激光器,其峰值发射波长处于中红外波段(2.5~25μm),具有功率高、线宽窄、响应速率快等传统半导体激光器所没有的独特优势,且具有较高的探测灵敏度,非常适合中红外波段的气体分子的检测。可广泛应用于大气痕量气体、呼吸气体、燃烧气体、生化气体、机动车尾气、工业废气以及农药残留气体等低浓度气体的检测。因此,利用量子级联激光器对气体分子进行探测在非侵入式医学诊断、环境监测以及工农业生产等领域都具有十分重要的意义。自20世纪末量子级联激光器发明以来,室温激光器的性能得到了长足的进步,也出现了多种结构形式的量子级联激光器。这也使得量子级联激光器红外吸收光谱技术得到了很大的发展。事实上,很多光谱技术在量子级联激光器发明之前就已经得到了发展和应用,而利用量子级联激光器作为光源则在很大程度上扩展了可探测波段,也在一定程度上提高了探测极限。这其中就包括了直接吸收光谱技术、波长调制技术、腔衰荡光谱技术、腔增强吸收光谱技术以及光声光谱等。综述了国内外量子级联激光器进行红外吸收光谱技术的研究现状和发展趋势,分析了量子级联激光器红外吸收光谱技术在发展过程中所遇到的瓶颈以及后期得到的解决方案,比较详细地介绍了各种方法的原理、应用,并指出了在吸收光谱测量中的优缺点,同时对外场痕量气体探测作了简要总结。最后,对量子级联激光器红外吸收光谱技术在未来痕量气体探测上的应用和发展进行了展望,指出随着红外吸收光谱技术的快速发展,这些方法可以得到更有效的改进和发展,进而朝着高灵敏度、高集成度以及高时效方向发展。

As a new type of unipolar semiconductor laser, the quantum cascade laser (QCL) has a peak emission wavelength in the mid-infrared band (2.5~25 μm), and has the unique advantages that traditional semiconductor lasers do not have, such as high power, narrow linewidth and fast response rate. The infrared absorptio n spectroscopy of QCLs has high detection sensitivity and is very suitable for the detection of gas molecules with the characteristic spectrum in the mid-infra red band and can be widely used in the detection of low-concentration gas such as trace gas, respiratory gas, combustion gas, biochemical gas, automobile e xhaust, industrial waste gas and pesticide residue gas. Therefore, the use of QCL to detect gas molecules is of great significance in non-invasive medical d iagnosis, environmental monitoring, and industrial and agricultural production . Since the invention of QCL at the end of 20th century, the performance of ro om temperature laser has been greatly improved, and a variety of QCLs have appe ared, which also makes the infrared absorption spectroscopy of QCLs gr eatly developed. In fact, many laser spectroscopies have been developed and ap plied before the invention of QCL. These include direct absorption spectroscopy (DAS), wavelength modulation spectroscopy (WMS), cavity ring-down spectrosco py (CRDS), cavity enhanced absorption spectroscopy (CEAS) and photoacoustic spe ctroscopy (PAS) and other related technologies. While the use of QCL as the lig ht source extends the detectable band to a large extent, and also increases the detection limit to some extent. This paper reviews the research status and dev elopment trends of infrared absorption spectroscopy of QCLs at home and abroad, and analyzes the bottlenecks encountered in the development process and the sol utions obtained in the later stage. The principle and application of various me thods are introduced in detail, and the advantages and disadvantages in the mea surement are pointed out. At the same time, the field trace gas detection is b riefly summarized. Finally, the application and development of infrared absorp tion spectroscopy of QCLs in the detection of trace gases in the future are pros pected. It is pointed out that with the rapid development of infrared absorptio n spectroscopy, these methods can be more effectively improved and developed wi th high sensitivity, high integration and high timeliness.