Surface-emitting THz sources based on difference-frequency generation in mid-infrared quantum cascade lasers

M. Geiser, C. Pflügl, A. Belyanin, Q. J. Wang, N. Yu, M. A. Belkin, T. Edamura, H. Kan, M. Fischer, A. Wittmann, J. Faist, Federico Capasso

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

3 Scopus citations


We report a surface-emitting THz source based on intracavity difference-frequency generation in dual-wavelength midinfrared quantum cascade lasers with integrated giant second-order nonlinear susceptibility. The THz light is coupled out of the waveguide by a second-order grating etched into the laser ridges. In contrast to sources where the difference-frequency radiation is emitted from the facet, this approach enables extraction of the THz emission from the whole length of the device even when the coherence length is small. We also studied the properties of the mid-infrared pump beams and found that due to gain competition, mid-infrared modes tend to start lasing in higher order lateral modes. The mid-infrared mode with the lower threshold current reduces population inversion for the second laser with the higher threshold current due to stimulated emission. We developed a rate equation model to quantitatively describe mode interactions due to mutual gain depletion.

Original languageEnglish
Title of host publicationNovel In-Plane Semiconductor Lasers IX
StatePublished - 2010
Externally publishedYes
EventNovel In-Plane Semiconductor Lasers IX - San Francisco, CA, United States
Duration: 25 Jan 201028 Jan 2010

Publication series

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


ConferenceNovel In-Plane Semiconductor Lasers IX
Country/TerritoryUnited States
CitySan Francisco, CA


  • Difference frequency generation
  • Frequency mixing
  • Gain competition
  • Mode competition
  • Multi-wavelength laser
  • Nonlinear optics
  • Quantum cascade laser
  • Surface emission
  • THz


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