Distributed feedback terahertz frequency quantum cascade lasers with dual periodicity gratings

TL;DR

This paper presents a novel design of terahertz quantum cascade lasers using double-periodicity gratings to independently control emission frequency and beam direction, enabling highly collimated and tunable THz emission.

Contribution

The authors introduce a dual periodicity grating design that allows independent control of emission frequency and beam angle in THz QCLs, using a wavevector scattering model.

Findings

Single mode THz emission with tunable angles between 0° and 50°

Achieved highly collimated THz emission

Demonstrated lithographically independent phase-matching approach

Abstract

We have developed terahertz frequency quantum cascade lasers that exploit a double-periodicity distributed feedback grating to control the emission frequency and the output beam direction independently. The spatial refractive index modulation of the gratings necessary to provide optical feedback at a fixed frequency and, simultaneously, a far-field emission pattern centered at controlled angles, was designed through use of an appropriate wavevector scattering model. Single mode THz emission at angles tuned by design between 0{\deg} and 50{\deg} was realized, leading to an original phase-matching approach, lithographically independent, for highly collimated THz QCLs.