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Title: Investigation of giant Kerr nonlinearity in quantum cascade lasers using mid-infrared femtosecond pulses

We study the Kerr nonlinearity of quantum cascade lasers (QCLs) by coupling resonant and off-resonant mid-infrared (mid-IR) femtosecond (fs) pulses into an active QCL waveguide. We observe an increase in the spectral width of the transmitted fs pulses as the coupled mid-infrared (mid-IR) pulse power increases. This is explained by the self-phase modulation effect due to the large Kerr nonlinearity of QCL waveguides. We further confirm this effect by observing the intensity dependent far-field profile of the transmitted mid-IR pulses, showing the pulses undergo self-focusing as they propagate through the active QCL due to the intensity dependent refractive index. We experimentally estimate the nonlinear refractive index n{sub 2} of a QCL to be ∼8 × 10{sup −9 }cm{sup 2}/W using the far-field beam profile of the transmitted pulses. The finite-difference time-domain simulations of QCL waveguides with Kerr nonlinearity incorporated show similar behavior to the experimental results.
Authors:
;  [1] ;  [2] ;  [3] ;  [1] ;  [2] ;  [2]
  1. Center for Advanced Studies in Photonics Research (CASPR), University of Maryland, Baltimore County (UMBC), 1000 Hilltop Circle, Baltimore, Maryland 21250 (United States)
  2. (UMBC), 1000 Hilltop Circle, Baltimore, Maryland 21250 (United States)
  3. Department of Physics, University of Maryland, Baltimore County (UMBC), 1000 Hilltop Circle, Baltimore, Maryland 21250 (United States)
Publication Date:
OSTI Identifier:
22420231
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 106; Journal Issue: 5; 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; BEAM PROFILES; INTERMEDIATE INFRARED RADIATION; NONLINEAR PROBLEMS; PULSES; REFRACTIVE INDEX; SEMICONDUCTOR LASERS; SIMULATION; WAVEGUIDES