Frequency combs in optically-injected terahertz ring quantum cascade lasers

TL;DR

This paper demonstrates the formation and control of frequency combs in ring terahertz quantum cascade lasers through optical injection from a DFB laser, highlighting potential for integrated, compact comb sources.

Contribution

It introduces a method to generate and manipulate frequency combs in ring terahertz QCLs using optical injection, enabling new integrated comb device designs.

Findings

Frequency combs can be selectively formed in ring QCLs.

Optical injection allows control over comb properties.

Potential for soliton generation and efficient power extraction.

Abstract

Quantum cascade lasers (QCLs) have emerged as promising candidates for generating chip-scale frequency combs in mid-infrared and terahertz wavelengths. In this work, we demonstrate frequency comb formation in ring terahertz QCLs using the injection of light from a distributed feedback (DFB) laser. The DFB design frequency is chosen to match the modes of the ring cavity (near 3.3 THz), and light from the DFB is injected into the ring QCL via a bus waveguide. By controlling the power and frequency of the optical injection, we show experimentally and theoretically that combs can be selectively formed and controlled in the ring cavity. The potential for soliton generation and efficient power extraction through the bus waveguide presents exciting opportunities for integrating this technology in compact comb designs.