Real-time gas density measurement using a ring cavity Terahertz parametric oscillator

S. Ohno, R. Guo, H. Minamide, H. Ito

Research output: Chapter in Book/Report/Conference proceedingConference contribution


We carried out real-time measurement of gas density using monochromatic terahertz waves. The THz-wave absorbance is useful to measure the density of a gas having a characteristic spectrum in the THz region. We used the ring cavity THz-wave parametric oscillator (ring-TPO) as a monochromatic tunable THz-wave source. One can change the oscillation frequency of ring-TPO with a rotating galvano mirror forming the ring cavity. The frequency can be changed by synchronization with a repeating pump-pulse of 500 Hz. We demonstrated real-time measurement of the gas density in R-22, which had some spectral structure in THz frequency region. The gas density in the sample cell was changed by controlling the pressure to lower than 1 atm. When the gas density in the cell was the most tenuous, the maximum sensitivity was about 5%, which was limited by the fluctuation of THz-wave intensity.

Original languageEnglish
Title of host publicationNonlinear Optics and Applications II
Publication statusPublished - 2007 Nov 19
Externally publishedYes
EventNonlinear Optics and Applications II - Prague, Czech Republic
Duration: 2007 Apr 162007 Apr 18

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X


OtherNonlinear Optics and Applications II
Country/TerritoryCzech Republic


  • Gas sensing
  • R-22
  • Terahertz parametric oscillator

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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