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Optical heterodyne detection for cavity ring-down spectroscopy

United States Patent

6,094,267
July 25, 2000
View the Complete Patent at the US Patent & Trademark Office
A cavity ring-down system for performing cavity ring-down spectroscopy (CRDS) using optical heterodyne detection of a ring-down wave E.sub.RD during a ring-down phase or a ring-up wave E.sub.RU during a ring up phase. The system sends a local oscillator wave E.sub.LO and a signal wave E.sub.SIGNAL to the cavity, preferably a ring resonator, and derives an interference signal from the combined local oscillator wave E.sub.LO and the ring-down wave E.sub.RD (or ring-up wave E.sub.RU). The local oscillator wave E.sub.LO has a first polarization and the ring-down wave E.sub.RD has a second polarization different from the first polarization. The system has a combining arrangement for combining or overlapping local oscillator wave E.sub.LO and the ring-down wave E.sub.RD at a photodetector, which receives the interference signal and generates a heterodyne current I.sub.H therefrom. Frequency and phase differences between the waves are adjustable.
Levenson; Marc D. (Saratoga, CA), Paldus; Barbara A. (Mountain View, CA), Zare; Richard N. (Stanford, CA)
The Board of Trustees of the Leland Stanford Jr. University (Palo Alto, CA)
09/ 295,213
April 21, 1999
U.S. GOVERNMENT RIGHTS This invention was made with U.S. Government support by the Department of Energy and the Air Force under grant numbers DE-FG03-92ER14304 and F49620-97-1-0316, respectively. The U.S. Government has certain rights in this invention.