Patent ID: 6134253
Filing Date: 2000-10-17
Classification: G02B,H01S

Abstract:
An apparatus for monitoring the wavelength of laser radiation, comprising:an optical beam splitting apparatus for splitting first and second split beams from a monitored beam having a monitored wavelength;a first optical filter responsive to said first split beam for producing therefrom a first filtered beam in accordance with a first spectral filter function;a second optical filter for producing, responsive to said second split beam, a second filtered beam in accordance with a second spectral filter function, said first and second spectral filter functions crossing at a crossing point wavelength;said first filter including a substrate having a filter layer thereon, said filter layer including at least one film layer having a dielectric constant differing from that of said substrate,a surface of one of said substrate and said filter layer disposed for receiving said first split beam at a nonzero angle of incidence, anda beam comparing element for comparing the intensities of said first and second filtered beams for producing an error signal responsive to the deviation of the wavelength of said monitored beam from a set point wavelength.