Long-wavelength (λ ≈ 12- 16 μm) and cascaded transition quantum cascade lasers

Xue Huang, Yenting Chiu, Jingyuan L. Zhang, William O. Charles, Vadim E. Tokranov, Serge Oktyabrsky, Claire F. Gmachl

Research output: Chapter in Book/Report/Conference proceedingConference contribution


Long-wavelength (12 - 16 μm) Quantum Cascade (QC) lasers are crucial devices for improving the detection sensitivity of QC-laser based sensing for important gases including BTEX (benzene, toluene, ethylbenzene, and xylenes) or uranium hexafluoride. A high-performance QC laser emitting at ∼ 14 μm is reviewed, optimized by employing a diagonal optical transition and a two-phonon-continuum depletion scheme. It shows a low threshold current density of 2.0 kA/cm2, a peak power of 336 mW, all at 300 K, as well as a high characteristic temperature ∼ 310 K over a wide temperature range around room temperature (240- 390 K). Single-mode operation is demonstrated with short cavities, with a mode-hop-free continuous tuning range of ∼ 5.5 cm-1. The ridge-width dependence of threshold of ∼ 14 μm QC lasers by both wet etching and dry etching is studied. The main challenge for narrowing wet-etched ridges is the high loss caused by mode coupling to surface plasmon modes at the insulator/metal interface of sloped sidewalls. Conversely, dryetched ridges avoid surface plasmon mode coupling due to the absence of transverse magnetic polarization for the vertical insulator and metal layers. To further improve the efficiency of QC lasers, a same-wavelength cascaded transition approach is developed, with two sequential cascaded transitions at the same wavelength ∼ 14.2 μm in each stage. This same-wavelength cascaded-transition QC gain medium was inserted between two conventional QC stacks at the same wavelength. Slope efficiency is increased by 46% when laser operation changes from the single-transition region to the cascaded-transition region.

Original languageEnglish (US)
Title of host publicationNovel In-Plane Semiconductor Lasers XII
StatePublished - 2013
EventNovel In-Plane Semiconductor Lasers XII - San Francisco, CA, United States
Duration: Feb 4 2013Feb 7 2013

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X


OtherNovel In-Plane Semiconductor Lasers XII
Country/TerritoryUnited States
CitySan Francisco, CA

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Applied Mathematics
  • Electrical and Electronic Engineering
  • Computer Science Applications


  • Intersubband
  • Mid-infrared
  • Quantum Cascade laser
  • Sensing


Dive into the research topics of 'Long-wavelength (λ ≈ 12- 16 μm) and cascaded transition quantum cascade lasers'. Together they form a unique fingerprint.

Cite this