Quantum cascade lasers for high-resolution spectroscopy

Despite the growing interest that quantum cascade lasers (QCLs) are gaining, they still present a few unclear aspects of their fundamental properties, such as spectral purity, that need to be deeply investigated when aiming to make these innovative laser sources suitable for high-resolution spectroscopy and metrology. This paper is a review of our efforts towards QCL-based high-resolution spectroscopy and of our experimental investigation of QCLs' frequency noise, aimed to discover the ultimate performances attainable by QCLs and to develop the exper- imental techniques required to achieve them. Our results, confirmed by several independent measurements, show that QCLs have a very small intrinsic linewidth buried under a large frequency-noise background. The development of appropriate frequency stabilization techniques will make QCLs well suited for high-resolution spectroscopy and metrology in the mid and far IR. C 2010 Society of Photo-Optical Instrumentation Engineers.

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