Spectroscopic techniques based on Distributed FeedBack (DFB) Quantum Cascade Lasers (QCL) provide good results for gas detection in the mid-infrared region in terms of sensibility and selectivity. The main limitation is the QCL relatively low tuning range (~10 cm⁻¹) that prevents from monitoring complex species with broad absorption spectra in the infrared region or performing multi-gas sensing. To obtain a wider tuning range, the first solution presented in this paper consists of the use of a DFB QCL array. Tuning ranges from 1335 to 1387 cm⁻¹ and from 2190 to 2220 cm⁻¹ have been demonstrated. A more common technique that will be presented in a second part is to implement a Fabry–Perot QCL chip in an external-cavity (EC) system so that the laser could be tuned on its whole gain curve. The use of an EC system also allows to perform Intra-Cavity Laser Absorption Spectroscopy, where the gas sample is placed within the laser resonator. Moreover, a technique only using the QCL compliance voltage technique can be used to retrieve the spectrum of the gas inside the cavity, thus no detector outside the cavity is needed. Finally, a specific scheme using an EC coherent QCL array can be developed. All these widely-tunable Quantum Cascade-based sources can be used to demonstrate the development of optical gas sensors.

中文翻译：

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基于理想可调量子级联的光源，用于光学气体传感器的开发

基于分布式反馈（DFB）量子级联激光器（QCL）的光谱技术在灵敏度和选择性方面为中红外区域的气体检测提供了良好的结果。QCL的主要局限性在于其相对较低的调谐范围（〜10 cm ^-1），无法监测红外范围内具有宽吸收光谱的复杂物质或进行多种气体检测。为了获得更大的调谐范围，本文提出的第一个解决方案包括使用DFB QCL阵列。调整范围是1335至1387 cm ^-1和2190至2220 cm ^-1已经证明。第二部分将介绍一种更常见的技术，即在外腔（EC）系统中实现Fabry-Perot QCL芯片，以便可以在整个增益曲线上调整激光器。EC系统的使用还允许执行腔内激光吸收光谱法，其中将气体样品放置在激光谐振器内。此外，仅使用QCL顺应电压技术的技术可用于检索腔体内气体的光谱，因此无需在腔体外部的检测器。最后，可以开发出使用EC相干QCL阵列的特定方案。所有这些基于量子级联的可广泛调谐的信号源都可用于演示光学气体传感器的发展。