Deflecting light into resonant cavities for spectroscopy

US5815277A · kind A · utility

Assignee

• The Board of Trustees of the Leland Stanford Junior University · US

Inventors

• Richard N. Zare · Stanford, US
• Juergen Martin · Singen, DE
• Barbara Paldus · Atherton, US

Key dates

• Filing date: Oct 10, 1997
• Grant date: Sep 29, 1998
• Expiry date: Oct 10, 2017

Classification

• Technology area (CPC G): Physics
• CPC primary: G01N21/39
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

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.