Active mode locking of quantum cascade lasers operating in external ring cavity

TL;DR

This paper demonstrates the first active mode locking of an external-cavity quantum cascade laser operating at room temperature, enabling ultrashort pulses in the mid-infrared range with potential for various applications.

Contribution

It introduces a novel active mode locking technique for quantum cascade lasers in an external cavity, achieving room-temperature operation.

Findings

Mode-locked regime achieved at room temperature

Operates over full injection current range

First demonstration of active mode locking in this system

Abstract

Stable ultrashort light pulses and frequency combs generated by mode-locked lasers have many important applications including high-resolution spectroscopy, fast chemical detection and identification, studies of ultrafast processes, and laser metrology. While compact mode-locked lasers emitting in the visible and near infrared range have revolutionized photonic technologies, the systems operating in the mid-infrared range where most gases have their strong absorption lines, are bulky and expensive and rely on nonlinear frequency down-conversion. Quantum cascade lasers are the most powerful and versatile compact light sources in the mid-infrared range, yet achieving their mode locked operation remains a challenge despite dedicated effort. Here we report the first demonstration of active mode locking of an external-cavity quantum cascade laser. The laser operates in the mode-locked regime at room temperature and over the full dynamic range of injection currents of a standard commercial laser chip.