Dispersion engineering of Quantum Cascade Lasers frequency combs

TL;DR

This paper demonstrates that integrating a Gires-Tournois Interferometer into quantum cascade lasers significantly improves their frequency comb performance, making them more suitable for compact spectroscopy applications.

Contribution

The study introduces a dispersion compensation scheme using a Gires-Tournois Interferometer to enhance QCL-comb operation and stability.

Findings

Improved comb stability and reduced phase noise.

Achieved >100 mW power with 70 cm$^{-1}$ bandwidth.

Enhanced suitability for chip-based spectroscopy.

Abstract

Quantum cascade lasers are compact sources capable of generating frequency combs. Yet key characteristics - such as optical bandwidth and power-per-mode distribution - have to be improved for better addressing spectroscopy applications. Group delay dispersion plays an important role in the comb formation. In this work, we demonstrate that a dispersion compensation scheme based on a Gires-Tournois Interferometer integrated into the QCL-comb dramatically improves the comb operation regime, preventing the formation of high-phase noise regimes previously observed. The continuous-wave output power of these combs is typically $>$ 100 mW with optical spectra centered at 1330 cm$^{-1}$ (7.52 $\mu$m) with $\sim$ 70 cm$^{-1}$ of optical bandwidth. Our findings demonstrate that QCL-combs are ideal sources for chip-based frequency comb spectroscopy systems.