Swept continuous wave cavity ring-down spectroscopy

US6466322B1 · kind B1 · utility

Assignee

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

Inventors

• Barbara Paldus · Atherton, US
• Richard N. Zare · Stanford, US

Key dates

• Filing date: Dec 23, 1999
• Grant date: Oct 15, 2002
• Expiry date: Dec 23, 2019

Classification

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

Abstract

An ring-down spectroscopy instrument comprising a ring-down cavity (RDC) and CW light source (CWLS). The CWLS produces light having components with different polarizations. The ring-down cavity is optically isolated from the light source so that light reflected from the cavity is precluded from perturbing the light source. A frequency shifter shifts a mean frequency of the first component of input light with respect to a mean frequency of the second component of input light by a frequency shift &Dgr;&ngr;. A first detector measures a signal beam with the a polarization. A second detector measures a tracking beam having a second polarization. The frequency shift &Dgr;&ngr; is equal to a difference between a resonant frequency of a first cavity mode with the first polarization and a resonant frequency of a second cavity mode having the second polarization. A threshold detector delivers a trigger pulse to the frequency shifter when an intensity of the signal beam reaches a predetermined value. The trigger pulse causes the frequency shifter to temporarily change the frequency shift &Dgr;&ngr;, thereby temporarily decoupling the first component of input light from the ring-down cavity. …