Patent ID: 7843977

Claim:
A light source that generates light of an output wavelength, said light source comprising: first and second lasers that emit first and second light beams, respectively, at wavelengths that are determined by first and second wavelength control signals, respectively; first and second beam splitters that split said first and second light beams, respectively, to create first and second sampling light beams, respectively; first and second wavelength control assemblies that receive said first and second sampling light beams, respectively, and generate said first and second wavelength control signals, respectively, such that said wavelengths of said first and second light beams differ by no more than a predetermined amount, said first and second wavelength control assemblies receiving said first and second sampling light beams, respectively, said first and second wavelength control assemblies each comprising: an absorption cell having a gas that has an optical absorption that varies with said wavelength of said first and second sampling light beams at wavelengths around said output wavelength; and a first photodetector that measures an intensity of light leaving that absorption cell; and an environmental control system that maintains said absorption cells in said first and second wavelength control assemblies at a predetermined temperature.