Effect of waveguide side-wall roughness on the performance of quantum cascade lasers

Fatima Toor, Deborah L. Sivco, Claire F. Gmachl

Research output: Contribution to journalConference articlepeer-review

1 Scopus citations


We report on a study to determine the effect of waveguide side-wall roughness on Quantum Cascade (QC) laser performance, such as threshold current density, slope efficiency, far-field beam pattern and group refractive index, using two two-wavelength heterogeneous cascade QC laser structures, one with emission wavelengths of 7.0 μm/11.2 μm and the other with 8.7 μm /12.0 μm For the range of roughness standard deviation values from about 0.4 μm to 1.0 μm for which all four QC lasers were operating, the threshold current density increases by 12%-15% and the slope efficiency decreases by 30%-70% with stronger performance degradation for the shorter wavelength lasers, which is in agreement with a model based on Rayleigh scattering. Moreover, no significant change in the far-field beam patterns for different σrough values was observed, and the group effective index values of the four wavelengths have several values for each rough waveguide indicative of multiple transverse modes in the waveguides.

Original languageEnglish (US)
Article number72301P
JournalProceedings of SPIE - The International Society for Optical Engineering
StatePublished - 2009
EventNovel In-Plane Semiconductor Lasers VIII - San Jose, CA, United States
Duration: Jan 26 2009Jan 29 2009

All Science Journal Classification (ASJC) codes

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


  • Multi-wavelength lasers
  • Quantum cascade lasers
  • Roughness
  • Semiconductor lasers
  • Waveguides


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