Frequency Control of a Mid-Infrared Quantum Cascade Laser Frequency Comb by Near-Infrared Light Injection and Intensity Modulation

Abstract

Mid-infrared (MIR) quantum cascade laser (QCL) frequency combs are a convenient technology for MIR dual comb spectroscopy. A common method to increase the signal-to-noise ratio in this type of applications is by mutual stabilization of the frequency combs. The mode spacing in a QCL comb can be injection-locked via electrical injection of a radio-frequency close to the repetition rate ( f rep ) [1] . The control of the comb offset frequency f o is typically done by adjusting the driving current or the temperature of the QCL. However, the tight-lock between two QCL combs has not yet been reported in literature. In this work, we demonstrate faster control over both degrees of freedom of a MIR QCL comb by optically injecting a near-infrared (NIR) laser into the QCL cavity, which could enable the tight-locking of two QCL combs.