3 February 2009 Effect of waveguide side-wall roughness on the performance of quantum cascade lasers
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Abstract
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.
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Fatima Toor, Deborah L. Sivco, Claire F. Gmachl, "Effect of waveguide side-wall roughness on the performance of quantum cascade lasers", Proc. SPIE 7230, Novel In-Plane Semiconductor Lasers VIII, 72301P (3 February 2009); doi: 10.1117/12.808227; https://doi.org/10.1117/12.808227
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