WAVELENGTH VARIABLE OPTICAL FILTER, LASER APPARATUS AND METHOD FOR STABILIZING LASER WAVELENGTH

摘要

PROBLEM TO BE SOLVED: To constantly and accurately detect the shift of a target wavelength to realize stable wavelength lock without being affected by the variation in the light output intensity of a laser beam source. SOLUTION: Two Fabry-perot resonators, in which transmission center wavelengths are different and the difference between the lengths of resonators are adjusted so that transmissions are equal within a range of 0.1-0.9 at an intermediate wavelength equally spaced from two transmission center wavelengths, are constructed by using a parallel flat base plates 7 having a step 7 and high reflectance layers 8 and 9 on both sides. An incident light is branched into two parts with a directional coupler 3 and the lights are incident one by one. The plate 7 rotates on a rotation stage 6 on which the plate 7 is arranged to control the lengths of the resonators, thereby varying the wavelength.