High-resolution (Doppler-limited) spectroscopy using quantum-cascade distributed-feedback lasers

S. W. Sharpe, J. F. Kelly, J. S. Hartman, C. Gmachl, F. Capasso, D. L. Sivco, J. N. Baillargeon, A. Y. Cho

Research output: Contribution to journalArticlepeer-review

113 Scopus citations


Lasing characteristics were evaluated for distributed-feedback quantum-cascade (QC) lasers operating in a continuous mode at cryogenic temperatures. These tests were performed to determine the QC lasers' suitability for use in high-resolution spectroscopic applications, including Doppler-limited molecular absorption and pressure-limited lidar applications. By use of a rapid-scan technique, direct absorbance measurements of nitric oxide (NO) and ammonia (NH3) were performed with several QC lasers, operating at either 5.2 or 8.5 μm. Results include time-averaged linewidths of better than 40 MHz and long-term laser frequency reproducibility, even after numerous temperature cycles, of 80 MHz or better. Tuning rates of 2.5 cm-1 in 0.6 ms can be easily achieved. Noise-equivalent absorbance of 3 × 10-6 was also obtained without optimizing the optical arrangement.

Original languageEnglish (US)
Pages (from-to)1396-1398
Number of pages3
JournalOptics Letters
Issue number17
StatePublished - Sep 1 1998
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Atomic and Molecular Physics, and Optics


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