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Title: Measurements and simulations of the optical gain and anti-reflection coating modal reflectivity in quantum cascade lasers with multiple active region stacks

We report spectrally resolved gain measurements and simulations for quantum cascade lasers (QCLs) composed of multiple heterogeneous stacks designed for broadband emission in the mid-infrared. The measurement method is first demonstrated on a reference single active region QCL based on a double-phonon resonance design emitting at 7.8 μm. It is then extended to a three-stack active region based on bound-to-continuum designs with a broadband emission range from 7.5 to 10.5 μm. A tight agreement is found with simulations based on a density matrix model. The latter implements exhaustive microscopic scattering and dephasing sources with virtually no fitting parameters. The quantitative agreement is furthermore assessed by measuring gain coefficients obtained by studying the threshold current dependence with the cavity length. These results are particularly relevant to understand fundamental gain mechanisms in complex semiconductor heterostructure QCLs and to move towards efficient gain engineering. Finally, the method is extended to the measurement of the modal reflectivity of an anti-reflection coating deposited on the front facet of the broadband QCL.
Authors:
 [1] ;  [2] ; ; ; ; ;  [3] ;  [1]
  1. Institute for Quantum Electronics, ETH-Zurich, CH-8093 Zurich (Switzerland)
  2. (Switzerland)
  3. Alpes Lasers SA, 1-3 Maximilien-de-Meuron, CH-2000 Neuchatel (Switzerland)
Publication Date:
OSTI Identifier:
22494818
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 118; Journal Issue: 9; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; COATINGS; COMPUTERIZED SIMULATION; DENSITY MATRIX; GAIN; LASERS; PHONONS; REFLECTION; REFLECTIVITY; RESONANCE; SCATTERING; SEMICONDUCTOR MATERIALS; STACKING FAULTS; THRESHOLD CURRENT