Waveguiding and dispersion properties of interband cascade laser frequency combs

L. A. Sterczewski, M. Bagheri, C. Frez, C. L. Canedy, I. Vurgaftman, M. Kim, C. S. Kim, C. D. Merritt, W. W. Bewley, J. Faist, G. Wysocki, J. R. Meyer

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Mid-infrared semiconductor lasers have emerged as indispensable compact coherent sources for military and commercial applications. While much of the historical emphasis has been on maximizing the output power and/or spectral purity, a recent new focus has been on engineering these lasers to operate as optical frequency combs (OFCs) for broadband real-time spectroscopy. In particular, the combination of low-drive-power and broad gain bandwidth has made interband cascade laser (ICL) OFCs an attractive complement to quantum cascade laser OFCs operating at longer wavelengths. Moreover, ICL combs can potentially be incorporated into fully-integrated dual-comb spectrometers that employ fast, room-temperature IC photodetectors processed on the same chip. However, the high refractive index of the ICL's GaSb substrate poses some challenges to the optical waveguiding. Because the modal index is considerably lower than that of the substrate, the optical field can penetrate the bottom cladding layer and leak into the GaSb, inducing wavelength-dependent interference that modifies the gain and group velocity dispersion (GVD) profiles. Even when the effect on lasing threshold is small, the comb properties can be adversely affected. Using the sub-threshold Fourier transform technique, we studied ICL combs with various ridge widths, substrate thicknesses, and center wavelengths. This allowed us to evaluate the effects of modal leakage on the GVD. We find that the resonant nature of the substrate modes induces oscillations, which affect both the spectral bandwidth and the phase-locking properties above threshold. Strategies to mitigate the GVD's undesired and unpredictable spectral variation will be presented.

Original languageEnglish (US)
Title of host publicationNovel In-Plane Semiconductor Lasers XX
EditorsAlexey A. Belyanin, Peter M. Smowton
PublisherSPIE
ISBN (Electronic)9781510642454
DOIs
StatePublished - 2021
EventNovel In-Plane Semiconductor Lasers XX 2021 - Virtual, Online, United States
Duration: Mar 6 2021Mar 11 2021

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
Volume11705
ISSN (Print)0277-786X
ISSN (Electronic)1996-756X

Conference

ConferenceNovel In-Plane Semiconductor Lasers XX 2021
Country/TerritoryUnited States
CityVirtual, Online
Period3/6/213/11/21

All Science Journal Classification (ASJC) codes

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

Keywords

  • interband cascade
  • optical mode
  • semiconductor laser

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