Spectral and modulation performance of quantum cascade lasers with application to remote sensing

Richard M. Williams, James F. Kelly, Steven W. Sharpe, John S. Hartman, Claire Gmachl, Federico Capasso, Deborah L. Sivco, James N. Baillargeon, Alfred Y. Cho

Research output: Contribution to journalConference articlepeer-review

7 Scopus citations


We have characterized the spectral noise density and frequency modulation performance of an 8.5 micron quantum-cascade diode (QC) laser operating continuously at liquid nitrogen temperatures. The phase noise is measured by fixing the laser frequency in the half-height region of a molecular resonance and measuring the fluctuations in absorbance; these fluctuations are then accurately converted into measurements in the fluctuations of the absolute frequency. A Fourier analysis of the intrinsic spectral/phase noise show a 1/f2 dependence up to the measurement bandwidth limit of approx. 1 MHz. The laser linewidth is < 1 MHz when measured over several milliseconds. Servo locking schemes will be discussed with the implication that QC laser sources can be stabilized to a high degree. The frequency modulation performance of a QC laser has been measured and synchronous detection of f, 2f and 3f absorption signals (nitrous oxide at 8.5 μm) has been achieved with direct modulation of the injection current.

Original languageEnglish (US)
Pages (from-to)11-22
Number of pages12
JournalProceedings of SPIE - The International Society for Optical Engineering
StatePublished - 1999
Externally publishedYes
EventProceedings of the 1999 Application of Tunable Diode and Other Infrared Sources for Atmospheric Studies and Industrial Processing Monitoring II - Denver, CO, USA
Duration: Jul 19 1999Jul 20 1999

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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