Open Access86% internal differential efficiency from 8 to 9 µm-emitting, step-taper active-region quantum cascade lasers
Author(s) -
Jeremy Kirch,
Chun Chieh Chang,
Colin Boyle,
Luke J. Mawst,
D. Lindberg,
T. Earles,
D. Botez
Publication year - 2016
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.24.024483
Subject(s) - cascade , laser , leakage (economics) , quantum efficiency , materials science , quantum tunnelling , optics , optoelectronics , physics , chemistry , chromatography , economics , macroeconomics
8.4 μm-emitting quantum cascade lasers (QCLs) have been designed to have, right from threshold, both carrier-leakage suppression and miniband-like carrier extraction. The slope-efficiency characteristic temperature T 1 , the signature of carrier-leakage suppression, is found to be 665 K. Resonant-tunneling carrier extraction from both the lower laser level (ll) and the level below it, coupled with highly effective ll-depopulation provide a very short ll lifetime (~0.12 ps). As a result the laser-transition differential efficiency reaches 89%, and the internal differential efficiency η id , derived from a variable mirror-loss study, is found to be 86%, in good agreement with theory. A study of 8.8 μm-emitting QCLs also provides an η id value of 86%. A corrected equation for the external differential efficiency is derived which leads to a fundamental limit of ~90% for the η id values of mid-infrared QCLs. In turn, the fundamental wallplug-efficiency limits become ~34% higher than previously predicted.