Quantum cascade laser roadmap

TL;DR

This roadmap reviews the recent advances, current challenges, and future directions in quantum cascade lasers, emphasizing their design, frequency combs, and applications in mid-infrared and terahertz photonics.

Contribution

It provides a comprehensive, organized overview of the state of QCL research, integrating developments across design, comb generation, and practical applications.

Findings

QCLs are reliable sources in mid-infrared and terahertz regions.

Self-starting optical frequency combs have been demonstrated with QCLs.

Key challenges include improving device performance and expanding application scope.

Abstract

Quantum cascade lasers (QCLs) are unipolar semiconductor lasers first demonstrated in 1994. Since then, they have played a central role in advancing mid-infrared and terahertz photonics, becoming among the most reliable light sources in these regions of the electromagnetic spectrum. Their importance is further reinforced by their ability to generate self-starting optical frequency combs, whose investigation is motivated both by fundamental physics and by a wide range of applications, including molecular spectroscopy and free-space optical communications. This Roadmap provides a unified overview of current advances and emerging directions in QCL research. The chapters are organized into three main sections: device design and technology; frequency combs and pulse formation; and applications of QCLs. Each chapter reviews the relevant background, summarizes the current state of the art, and identifies key challenges and future directions within its specific research area.