Strongly modulated QCLs as broadband Mid-IR sources

Abstract

Quantum cascade lasers frequency combs (QCL-FC) have proven to be fundamental sources in the mid-infrared (Mid-IR) spectral region to perform spectroscopy on a wide range of molecules[1], [2]. However, they are still limited to a maximum of ∼ 100cm −1 [3], which impacts very strongly the possible applications in spectroscopy. For this reason, the challenge of finding new ways of operating QCLs for a broadband operation is of great interest. It has already been proved that by modulating the operation current of the devices with a radio-frequency (RF) signal the stability [4] and the emission bandwidth [5] of the comb can be substantially improved. Following this line of work, a study on the impact of strong RF injection (around 1W) at low frequencies compared to the typical repetition frequency of the device (between 0.8 and 1 GHz) has been performed.