Femtosecond pulses from a mid-infrared quantum cascade laser

TL;DR

This paper demonstrates a novel method to generate near-transform-limited sub-picosecond pulses with high peak power from a mid-infrared quantum cascade laser, overcoming previous limitations of pulse duration and power.

Contribution

It introduces an external pulse compression technique starting from a phase-locked state to produce ultrashort, high-power mid-IR pulses, expanding potential applications.

Findings

Achieved sub-picosecond pulses with several watts peak power

Developed a novel optical sampling method for pulse assessment

Demonstrated the feasibility of ultrashort pulse generation in mid-IR QCLs

Abstract

The quantum cascade laser (QCL) has evolved to be a compact, powerful source of coherent mid-infrared (mid-IR) light. However, its fast gain dynamics strongly restricts the formation of ultrashort pulses. As such, the shortest pulses reported so far were limited to a few picoseconds with some hundreds of milliwatts of peak power, strongly narrowing their applicability for time-resolved and nonlinear experiments. Here, we demonstrate an alternative approach capable of producing near-transform-limited sub-picosecond pulses with several watts of peak power. Starting from a frequency modulated phase-locked state, which most efficiently exploits the gain of the active region, ultrashort high peak power pulses are generated via external pulse compression. We assess their temporal nature by means of a novel optical sampling method, coherent beat note interferometry and interferometric autocorrelation. These results open new pathways for nonlinear physics in the mid-infrared.