Dual-Etalon Frequency-Comb Spectrometer

Absorption spectroscopy is the most quantitative and straightforward means of measuring the concentration and temperature of a species having a known spectrum. The primary criteria associated with using absorption spectroscopy, as an everyday tool for identifying environmental contaminates, are that large spectral bandwidths with good resolution are needed and high sensitivity is required. Sandia researchers have developed a compact, simple spectrometer that will allow doing both high resolution and broad bandwidth spectroscopy simultaneously within only a few microseconds and requiring no special light source or electronics.

The dual-etalon frequency-comb spectrometer is a novel, compact, low-cost spectrometer with limited moving parts. Sandia’s new absorption-based spectrometer is capable of both high sensitivity and broad bandwidth coverage with high spectral resolution. The broadband light source (e.g., pulsed laser, LED, lamp) is split into two beam paths. One light travels through an etalon and a sample gas, while the other travels through the second arm of an etalon cavity, and the two beams are recombined onto a single detector. The resulting interference pattern is Fourrier transformed to recover the spectrum of the sample. It has the high resolution over a broad bandwidth that is needed for chemical fingerprinting and the sensitivity of cavity ring-down spectroscopy.

Benefits

• Compact
• Low cost
• High sensitivity necessary to detect dilute species
• Broadband absorption spectropscopy
• Simultaneously measures absorption spectrum at multiple frequencies

Applications and Industries

• Point sensor for monitoring combustion by-products, environmental pollutants, and warfare agents
• Identification of unknown gases, liquids, and aerosols in either the laboratory or real-world applications
• Monitoring of multiple species in reaction flow streams
• Time-resolved multispectral imaging with nanosecond time resolution