Cavity ring-down apparatus and method for measuring reflectivity of highly reflective mirrors

US7679750B2 · kind B2 · utility

Assignee

• Institute of Optics and Electronics, Chinese Academy of Sciences · CN

Inventors

• Bincheng Li · Zhenjiang, CN
• Yuan Gong · 安丰镇, CN

Key dates

• Filing date: Jul 18, 2008
• Grant date: Mar 16, 2010
• Expiry date: Oct 13, 2028

Classification

• Technology area (CPC G): Physics
• CPC primary: G01M11/005
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

A cavity ring-down apparatus and method is provided for measuring the reflectivity of highly reflective mirrors. The apparatus comprises an optical ring-down cavity including three highly-reflective mirrors whose frequency-selective optical transmission is retro-reflected into the oscillator cavity of a continuous-wave semiconductor laser, creating a change of output spectrum of said laser and enhancing the coupling coefficient of the laser power into the optical ring-down cavity. The drive current/voltage of the semiconductor laser is modulated by a square-wave function output by a function generation card. Thus the laser beam is suddenly switched off at the negative step of the square-wave signal periodically. Immediately after switching off the laser beam, an exponential decay signal of the ring-down cavity is measured by a photo detector and used to determine the decay time of the cavity and the reflectivity of highly reflective mirrors.