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Compact Near-IR and Mid-IR Cavity Ring Down Spectroscopy Device

Technology #006-000x-miller-u

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J. Houston Miller, Professor of Chemistry
Professor Miller's lab primarily develops and applies laser diagnostics to the analysis of problems in combustion science, atmospheric chemistry, and biotechnology. In addition, we have published several papers in the field of the structure and optical properties of polynuclear aromatic hydrocarbons and their aggregates.
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US Patent US 7,541,586
A continuous-Wave optical parametric oscillator for . . . mid infrared photoacoustic trace gas detection
N/A , Oct 2004

Compact Near-IR and Mid-IR Cavity Ring Down Spectroscopy Device

There are many technologies available for measuring trace amount of gas species, but there are tradeoffs between accuracy, sensitivity, selectivity, size and cost. For example, while tunable diode laser absorption spectroscopy may provide easily-interpreted spectrums for many gas species, this method generally can be orders of magnitude less sensitive than laboratory equipment such as GC/MS. On the other hand, while GC/MS is accurate, the equipment maybe too bulky, costly, and unable to withstand vibration and shock in a field environment.

Therefore, for many industrial applications, there is a need for a small sized field spectrometer that can accurately measure trace species of sample gases at a reasonable cost, equipment size, and power consumption.

GW researchers have developed a compact cavity ring down spectrometer that can measure trace amount of toxic gases at field environments. The spectrometer may use a tunable solid-state continuous mid-infrared laser, which are sensitive to many gases. An acousto-optic modulator, used as a “switch” for the laser, helps to interrupt laser beam when resonance is achieved. A specially designed resonant cavity may comprise of high-reflectivity mirrors in a bow-tie configuration. A piezo-transducer drive modulator can be used to maintain resonance between laser frequency and cavity modes, while a photo detector receives and generates signals and measures an interaction between the laser beam and sample gas. Furthermore, these researchers developed a method for extracting valuable data, filtering out noise, and thus providing an accurate and timely reading.

This spectrometer device can be uniquely compact and portable, and having a low power consumption. The device can measure trace amount of gaseous species such as HCHO, H2S, methy mercaptan, CO2, CO, HCN, NH3, C2H2, sarin, VX, mustard gas, arsine, phosgene, tear gas, pepper gas, nitrogen based explosives, and incapacitating agents such as B2. Therefore, the spectrometer device can be installed on aircraft, commercial building HVAC systems, public transportation systems, for both accurate fire and toxic gas detection. 

Researchers have patented various designs for this novel spectrometer.


  • Detecting Trace Amount of Gases


  • Can be used in field environments for continuous gas monitoring
  • Accurate, sensitive to large species of toxic gases, and requires low power.