Abstract

Optical frequency combs, which represent lasers whose spectrum consists of a set of evenly spaced modes with an unambiguous phase relationship, have proven themselves as a high-precision tool for spectroscopy in the last decade. Since the quantum cascade laser (QCL) has become the dominant laser source in the mid-infrared portion of the electromagnetic spectrum, where fundamental absorption lines of many molecules lie, it is of great use particularly in spectroscopy applications. Furthermore, a substantial third-order non-linearity in the laser active region results in phase-locking of the cavity modes and frequency comb generation without any need for additional optical components [1], making QCL based frequency combs an extremely active research topic.

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