Abstract

Mid-infrared quantum cascade lasers (QCLs) are widely used in numerous spectroscopic applications, e.g. in trace gas sensing. The long-term reliability of a spectroscopic gas sensor strongly relies on the emission wavelength stability of the QCL source. Hence, it is important to study how the emission frequency of a QCL behaves over long timescales. Other spectral properties such as the QCL frequency noise and associated linewidth and their long-term behavior are also essential in many applications. However, so far, most work focused on the short-term properties and no detailed long-term study has been presented. In this work, we present the first experimental study of the frequency stability of a QCL continuously assessed over a period of two months. In addition, we also investigated a possible change in the noise properties of the laser during the same period by regularly measuring its voltage flicker noise, which constitutes the main contributor to the laser frequency noise and represents a powerful mean to investigate noise processes in QCLs [1-2].

© 2015 IEEE