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Deflecting light into resonant cavities for spectroscopy

United States Patent

September 29, 1998
View the Complete Patent at the US Patent & Trademark Office
Light is coupled into a cavity ring down spectroscopy (CRDS) resonant cavity using an acousto-optic modulator. The AOM allows in-coupling efficiencies in excess of 40%, which is two to three orders of magnitude higher than in conventional systems using a cavity mirror for in-coupling. The AOM shutoff time is shorter than the roundtrip time of the cavity. The higher light intensities lead to a reduction in shot noise, and allow the use of relatively insensitive but fast-responding detectors such as photovoltaic detectors. Other deflection devices such as electro-optic modulators or elements used in conventional Q-switching may be used instead of the AOM. The method is particularly useful in the mid-infrared, far-infrared, and ultraviolet wavelength ranges, for which moderately reflecting input mirrors are not widely available.
Zare; Richard N. (Stanford, CA), Martin; Juergen (Harxheim, DE), Paldus; Barbara A. (Stanford, CA)
The Board of Trustees of the Leland Stanford Junior Univesity (Stanford, CA)
08/ 949,242
October 10, 1997
U.S. GOVERNMENT RIGHTS This invention was made with U.S. Government support under grant No. DE-FG03-92ER14304, awarded by the Department of Energy. The U.S. Government has certain rights in this invention.