title: Spectroscopic study of transparency current in mid-infrared quantum cascade lasers.
abstract: We report measurements which give direct insight into the origins of the transparency current for λ ~5 µm In0.6Ga0.4As/In0.42Al0.58As quantum cascade lasers in the temperature range of 80-280 K. The transparency current values have been found from broadband transmission measurements through the laser waveguides under sub-threshold operating conditions. Two active region designs were compared. The active region of the first laser is based on double-LO-phonon relaxation approach, while the second device has only one lower level, without specially designed resonant LO-phonon assisted depopulation. It is shown that transparency current contributes more than 70% to the magnitude of threshold current at high temperatures for both designs.
authors.affiliation: Department of Physics and Astronomy, The University of Sheffield, Sheffield, UK. d.revin@sheffield.ac.uk
authors.forename: Dmitry G
authors.initials: DG
authors.lastname: Revin
authors.forename: Randa S
authors.initials: RS
authors.lastname: Hassan
authors.forename: Andrey B
authors.initials: AB
authors.lastname: Krysa
authors.forename: Yongrui
authors.initials: Y
authors.lastname: Wang
authors.forename: Alexey
authors.initials: A
authors.lastname: Belyanin
authors.forename: Kenneth
authors.initials: K
authors.lastname: Kennedy
authors.forename: Chris N
authors.initials: CN
authors.lastname: Atkins
authors.forename: John W
authors.initials: JW
authors.lastname: Cockburn
mesh_terms: D017076:Computer-Aided Design; D004867:Equipment Design; D019544:Equipment Failure Analysis; D007259:Infrared Rays; D007834:Lasers; D011789:Quantum Theory; D013055:Spectrophotometry, Infrared / Q000295:instrumentation*; D020349:Surface Plasmon Resonance / Q000295:instrumentation*