Recent results in quantum cascade lasers and intersubband transitions in GaN/AlGaN multiple quantum wells

C. Gmachl, H. M. Ng, R. Paiella, R. Martini, H. Y. Hwang, D. L. Sivco, F. Capasso, A. Y. Cho, S. V. Frolov, S. N. George Chu, H. C. Liu

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


Quantum cascade (QC) lasers have been fabricated with Ge0.25Se0.75 chalcogenide lateral waveguide claddings. Aside from a strongly (up to ∼50%) reduced waveguide loss this device lay-out also displays a significantly reduced stray capacitance and improved high-speed modulation properties. This has been exploited for the first use of QC lasers in optical wireless communications as well as for gain-switched and actively mode-locked QC-lasers. Optical devices based on intersubband (IS) transitions face a rising interest also in other wavelength ranges due to their anticipated ultrafast electron dynamics. We present initial measurements of IS-transitions in the fiber-optics wavelength range in GaN/AlGaN samples grown by molecular beam epitaxy. IS-absorption at wavelengths of 1.44, 1.41, and 1.52 μm are measured for 11, 12, and 13 Å wide GaN quantum wells, respectively. We also measured the IS electron scattering time by conventional pump-probe technique. Using 1.55 μm as pump- and 1.70 μm as probe-wavelength, we obtain an electron scattering time of 370 fs.

Original languageEnglish (US)
Pages (from-to)823-828
Number of pages6
JournalPhysica E: Low-Dimensional Systems and Nanostructures
Issue number2-4
StatePublished - Mar 2002
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Atomic and Molecular Physics, and Optics
  • Condensed Matter Physics


  • GaN/AlGaN
  • Intersubband
  • Mid-infrared
  • Quantum cascade lasers


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