Patent ID: 7259860
Filing Date: 2007-08-21
Classification: G01B,G01J,H01S

Abstract:
1. A beam monitoring system for a mode-selective tuner comprising: a beamsplitter for diverting a portion of each of a plurality of measuring beams that are output from the mode-selective tuner at different frequency modes; a distance-shifting interferometer for producing interference patterns at each of the different frequency modes and having a pair of reference surfaces that establish (a) a nominal optical path length difference between interfering parts of the diverted measuring beam portion and (b) a variation in the nominal optical path length difference between corresponding points on the two reference surfaces spanning nearly at least one fringe of the interference patterns; a detector that samples the interference patterns at the corresponding points on the two reference surfaces; and a processor that converts variations in the interference patterns into measures of beam frequency variation; wherein the different frequency modes of the mode-selective tuner have a first free spectral range, the nominal optical path length difference between corresponding points on the two reference surfaces has a second free spectral range, and the first and second free spectral ranges are related by an integer multiple.