186 K operation of terahertz quantum-cascade lasers based on a diagonal design

TLDR

The study aims to increase upper‑state lifetime and gain at elevated temperatures by employing a diagonal design to achieve record temperature performance. The diagonal design is quantified by a radiative oscillator strength reduced by a factor of two compared to earlier designs. Resonant‑phonon terahertz quantum‑cascade lasers with a diagonal design reach 186 K heat‑sink temperature, deliver 63 mW peak power at 5 K and about 5 mW at 180 K, and operate at lower current densities due to reduced parasitic leakage.

Abstract

Resonant-phonon terahertz quantum-cascade lasers operating up to a heat-sink temperature of 186 K are demonstrated. This record temperature performance is achieved based on a diagonal design, with the objective to increase the upper-state lifetime and therefore the gain at elevated temperatures. The increased diagonality also lowers the operating current densities by limiting the flow of parasitic leakage current. Quantitatively, the diagonality is characterized by a radiative oscillator strength that is smaller by a factor of two from the least of any previously published designs. At the lasing frequency of 3.9 THz, 63 mW of peak optical power was measured at 5 K, and approximately 5 mW could still be detected at 180 K.