Minimal group refractive index dispersion and gain evolution in ultra-broad-band quantum cascade lasers

Claire Gmachl, Alex Soibel, Raffaele Colombelli, Deborah L. Sivco, Federico Capasso, Alfred Y. Cho

Research output: Contribution to journalArticlepeer-review

11 Scopus citations

Abstract

The group refractive index dispersion in ultra-broad-band quantum cascade (QC) lasers has been determined using Fabry-Pérot spectra obtained by operating the lasers in continuous wave mode below threshold. In the wavelength range of 5-8 μm, the global change of the group refractive index is as small as +8.2 × 10-3 μm-1 Using the method of Hakki and Paoli, the subthreshold gain of the lasers has furthermore been measured as a function of wavelength and current. At the wavelength of best performance, 7.4 μm, a modal gain coefficient of 16 cm·kA-1 at threshold and a waveguide loss of 18 cm-1 have been estimated. The gain evolution confirms an earlier assumption that cross-absorption restricted laser action to above 6 μm wavelength.

Original languageEnglish (US)
Pages (from-to)1671-1673
Number of pages3
JournalIEEE Photonics Technology Letters
Volume14
Issue number12
DOIs
StatePublished - Dec 1 2002
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Atomic and Molecular Physics, and Optics
  • Electrical and Electronic Engineering

Keywords

  • Mid-infrared
  • Quantum cascade (QC) laser
  • Semiconductor lasers
  • Semiconductor waveguides
  • Waveguide measurements

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