Patent ID: 9647411
Date: 2017-05-09
CPC Classifications: H01S

Claim:
1. A method of controlling a wavelength of a laser beam, comprising: measuring a relative wavelength of the laser beam with respect to a reference wavelength by using a spectroscope; controlling a line narrowing module based on a difference between a target wavelength and a sum of the relative wavelength and the reference wavelength, so as to change the wavelength of the laser beam by the difference; measuring an absolute wavelength of the laser beam at a first interval by using an absolute wavelength detector; and adjusting the reference wavelength of the laser beam at a second interval that is shorter than the first interval; wherein the adjusting the reference wavelength of the laser beam includes obtaining a gradient by calculating a difference between the reference wavelength and the absolute wavelength of the laser beam for the first interval, and adjusting the reference wavelength of the laser beam based on a value obtained by multiplying the gradient by the second interval.