Patent ID: 7733492

Claim:
A Sagnac interferometer, comprising: a beamsplitter arranged to receive an input beam of light having different wavelengths λ 1 and λ 2 , and split said input beam into first and second beams that travel along first and second paths, respectively, said first and second beams recombining along an output beam path; a first grating arranged so as to diffract the first beam, said first grating oriented to provide a first incident angle and a first diffraction angle for the wavelength, λ 1 , and to provide a first incident angle and a first diffraction angle for the wavelength, λ 2 , in said first beam, the first diffraction angle for both of said wavelengths, λ 1 and λ 2 , depending on the respective first incident angles and the respective wavelengths, the first incident angle and the first diffraction angle for both of said wavelengths, λ 1 and λ 2 , being displaced to the same side of a line normal to the first grating; and a second grating arranged so as to diffract the first beam after being diffracted by the first grating, said second diffraction grating oriented to provide a second incident angle and a second diffraction angle for said wavelength, λ 1 , and to provide a second incident angle and a second diffraction angle for said wavelength, λ 2 , such that said second incident angle for both of said wavelengths, λ 1 and λ 2 , depends on the respective first diffraction angles, and the second diffraction angle for both of said wavelengths, λ 1 and λ 2 , depends on the respective second incident angles and the respective wavelengths, wherein said first and second gratings are oriented so that the second diffraction angle for the wavelength, λ 1 , is different from the second diffraction angle for the wavelength, λ 2 , the difference including (i) a first contribution caused by the difference in the respective wavelengths on the diffraction of the first beam by the second grating and (ii) a second contribution caused by a difference in the respective second incident angles resulting from the difference in the respective first diffraction angles, said first contribution reinforcing the second contribution.