Low loss prism retroreflectors for relative index of refraction less than the square root of 2

US6172824A · kind A · utility

Assignee

• THE TRUSTEES OF PRINCETON UNIVERSITY · US

Inventors

• Kevin K. Lehmann · Crozet, US
• Paul Rabinowitz · Old Bethpage, US

Key dates

• Filing date: Jan 24, 2000
• Grant date: Jan 9, 2001
• Expiry date: Jan 24, 2020

Classification

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

Abstract

A stable resonator for a ring-down cavity spectroscopy cell having an optic axis. The resonator includes two Brewster's angle retroreflector prisms, at least one prism having greater than two total internal reflection surfaces. The prisms are disposed in alignment along the optic axis of the resonator. One or both of the prisms can be rotated so that light rays enter and leave a surface of the prism nearly at Brewster's angle to the normal of the prism surface. This feature maintains alignment between the prisms and allows the resonator to be tuned. One of the total internal reflection surfaces of at least one of the prisms may be a curved surface (either a ground curved surface or a surface curved by the addition, through optically contacting or gluing, of a plano-convex lens to the surface). In a preferred embodiment, at least one of the prisms has an apex angle of about 180.degree. minus two times Brewster's angle, a second angle of about 90.degree. plus the angle of incidence minus Brewster's angle, and a third angle of about three times Brewster's angle plus the angle of incidence for internal reflection minus 90.degree..