Tunable distributed-feedback quantum-cascade lasers for gas sensing applications

Claire Gmachl, Federico Capasso, Jérôme Faist, Deborah L. Sivco, James N. Baillargeon, Albert L. Hutchinson, Alfred Y. Cho, Khosrow Namjou-Khaless, Simin Cai, Edward A. Whittaker, James F. Kelly, Steven W. Sharpe, John S. Hartman

Research output: Contribution to journalConference articlepeer-review


Continuously tunable single-mode emission of high performance quantum cascade (QC) lasers is achieved by application of the distributed feedback (DFB) principle. The devices are fabricated either as loss-coupled or index-coupled DFB lasers. Single-mode tuning ranges of ≈ 100 nm have been measured in both of the atmospheric windows at emission wavelengths around λ ≈ 5 μm and 8 μm. Linear thermal tuning coefficients of 0.35 nm/K and 0.55 nm/K have been obtained above 200 K for λ ≈ 5 μm and 8 μm, respectively. The side-mode suppression ratio is better than 30 dB. Pulsed single-mode operation has been achieved up to room temperature with peak power levels of 60 mW. The lasers also operated single-mode in continuous wave at temperatures above liquid Nitrogen temperature; a single-mode tuning range of 70 mn has been measured in the temperature range from 20 K to 120 K. The gas sensing capabilities of the QC-laser have also been demonstrated using both direct absorption and wavelength modulation techniques. A pulsed, room temperature, QC-DFB laser operating at λ ≈ 7.8 μm was used to detect N2O diluted in N2. The detection limit was found to be ≈ 500 ppb-m. In addition, the high resolution capability of the QC-DFB lasers (at 77 K) has been demonstrated via continuous, rapid-scan, direct absorption measurement of the Doppler limited R(16.5) lambda doublet of NO at λ ≈ 5.2 μm.

Original languageEnglish (US)
Pages (from-to)144-153
Number of pages10
JournalProceedings of SPIE - The International Society for Optical Engineering
StatePublished - 1998
Externally publishedYes
EventFabrication, Testing and Reliability of Semiconductor Lasers III - San Jose, CA, United States
Duration: Jan 29 1998Jan 30 1998

All Science Journal Classification (ASJC) codes

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


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