Sub-Doppler resolution molecular spectroscopy in the 1.66-μm region

C. Ishibashi, K. Suzumura, H. Sasada

Research output: Contribution to journalConference articlepeer-review

1 Citation (Scopus)


We constructed a widely tunable spectrometer with sub-Doppler resolution and high sensitivity in the 1.66-μm region using a Fabry-Perot cavity as an absorption cell and a low-power extended-cavity laser diode as a light source. The light electric field is enhanced at the antinodes of the standing wave in the cavity cell, which enabled observation of saturated absorption spectra of the molecular overtone bands even though their transition dipole moments are small. The spectrometer sensitivity was drastically enhanced using a frequency modulation technique. The attained sensitivity allowed us to reduce sample gas pressure, optical power, and modulation amplitude, which resulted in a resolution of 320 kHz. We applied the spectrometer to precise frequency measurements of the 2ν3-band transitions of methane, and determined 66 frequency differences between them and two absolute frequencies with an accuracy of 40 and 600 kHz, respectively. We also recorded hyperfine-resolved spectrum of the 2ν4 band of methyl iodide, which gave unambiguous assignments.

Original languageEnglish
Pages (from-to)32-40
Number of pages9
JournalProceedings of SPIE - The International Society for Optical Engineering
Publication statusPublished - 2001
EventLaser Frequency Stabilization, Satandards, Measurement, and Applications - San Jose, CA, United States
Duration: 2001 Jan 242001 Jan 26


  • Diode laser
  • High resolution spectroscopy
  • High sensitivity
  • Molecular overtone band
  • Near infrared region

ASJC Scopus subject areas

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


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