Fourier Transform Infrared Phase Shift Cavity Ring Down Spectrometer

EPA Contract Number: EPD11038
Title: Fourier Transform Infrared Phase Shift Cavity Ring Down Spectrometer
Investigators: Dupuis, Julia Rentz
Small Business: OPTRA Inc.
EPA Contact: Manager, SBIR Program
Phase: I
Project Period: March 1, 2011 through August 31, 2011
Project Amount: $79,638
RFA: Small Business Innovation Research (SBIR) - Phase I (2011) RFA Text |  Recipients Lists
Research Category: SBIR - Air Pollution , Small Business Innovation Research (SBIR)


OPTRA proposes a Fourier transform phase shift cavity ring down spectroscopy (FT-PS-CRDS) system for high sensitivity detection of air toxic compounds. OPTRA's system operates in the 400-4000 cm-1 spectral range wherein lie vapor phase resonance bands for most air toxic compounds and hazardous chemicals; the spectral resolution is 4 or 16 cm-1, depending on the discrimination requirements. OPTRA's approach differs from previous FT-PS-CRDS systems as OPTRA has eliminated the external modulator and lock-in detection electronics. Historically, these systems measure a phase delay incurred by light traversing a resonant cavity; the phase delay is proportional to the product of the ring down time and the modulation frequency. Instead, OPTRA measures the spectrally dependent phase delay of the modulation frequencies imposed by the interferometer itself. OPTRA's approach is simpler that previous FT-PS-CRDS systems and represents a significant cost reduction without the eternal modulator. In addition, this approach produces the entire FT-PS­-CRDS spectra in a single rapid scan, making the technique truly real-time and significantly faster than previous techniques. Based on radiometric projections, OPTRA's FT-PS-CRDS system will be capable of ppb detection limits with an integration time of 1 second.

Under the Phase I effort, OPTRA will design, build, and test a breadboard FT-PS-CRDS system operating in the 700-1400 cm-1 spectral range to establish the feasibility of the proposed approach. Phase II plans will include the extension of the spectral range and the development of a full scale prototype. The Phase II also will address automated multicomponent algorithms.

Potential commercial applications include high sensitivity detection of air toxic compounds, chemical warfare agents, and other hazardous chemicals; industrial monitoring; and environmental sensing.





Progress and Final Reports:

  • Final Report
  • SBIR Phase II:

    Fourier Transform Infrared Phase Shift Cavity Ring Down Spectrometer