Multidimensional conduction-band engineering for maximizing the continuous-wave (CW) wallplug efficiencies of mid-infrared quantum cascade lasers

Dan Botez, Jae Cheol Shin, Jeremy Daniel Kirch, Chun Chieh Chang, Luke James Mawst, Thomas Earles

Research output: Contribution to journalArticlepeer-review

33 Citations (Scopus)

Abstract

By tailoring the active-region quantum wells and barriers of 4.5-5.0-μm-emitting quantum cascade lasers (QCLs), the device performances dramatically improve. Deep-well QCLs significantly suppress carrier leakage, as evidenced by high values for the threshold-current characteristic temperature T0 (253 K) and the slope-efficiency characteristic temperature T 1 (285 K), but, due to stronger quantum confinement, the global upper-laser-level lifetime τ4g decreases, resulting in basically the same room-temperature (RT) threshold-current density Jth as conventional QCLs. Tapered active-region (TA) QCLs, devices for which the active-region barrier heights increase in energy from the injection to the exit barriers, lead to recovery of the τ4g value while further suppressing carrier leakage. As a result, experimental RT Jth values from moderate-taper TA 4.8-μm emitting QCLs are ∼14% less than for conventional QCLs and T1 reaches values as high as 797 K. A step-taper TA (STA) QCL design provides both complete carrier-leakage suppression and an increase in the τ4g value, due to Stark-effect reduction and strong asymmetry. Then, the RT Jth value decreases by at least 25% compared to conventional QCLs of same geometry. In turn, single-facet, RT pulsed and continuous-wave maximum wallplug-efficiency values of 29% and 27% are projected for 4.6-4.8-μm-emitting QCLs.

Original languageEnglish
Article number6400209
JournalIEEE Journal on Selected Topics in Quantum Electronics
Volume19
Issue number4
DOIs
Publication statusPublished - 2013
Externally publishedYes

Keywords

  • Lasers
  • quantum wells (QWs)
  • quantum-well lasers
  • semiconductor lasers
  • Stark effect

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics
  • Electrical and Electronic Engineering

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