Reversible Mode Switching in Y coupled Terahertz Lasers

TL;DR

This paper demonstrates reversible, dual-frequency switching in coupled terahertz quantum cascade lasers using a hologram-designed grating, enabling controlled emission at specific THz frequencies through optical coupling.

Contribution

It introduces a novel method for reversible mode switching in coupled THz QCLs using a hologram-based grating integrated into one laser, transferred via evanescent coupling.

Findings

Achieved dual-frequency, electronically switchable emission in a QCL.

Demonstrated reversible transfer of switching behavior to an unmodified QCL.

Controlled THz emission at 2.88 and 2.92 THz frequencies.

Abstract

Electrically independent terahertz (THz) quantum cascade lasers (QCLs) are optically coupled in a Y configuration. Dual frequency, electronically switchable emission is achieved in one QCL using an aperiodic grating, designed using computer-generated hologram techniques, incorporated directly into the QCL waveguide by focussed ion beam milling. Multi-moded emission around 2.9 THz is inhibited, lasing instead occurring at switchable grating-selected frequencies of 2.88 and 2.92 THz. This photonic control and switching behaviour is selectively and reversibly transferred to the second, unmodified QCL via evanescent mode coupling, without the transfer of the inherent grating losses.