Patent ID: 7088513
Filing Date: 2006-08-08
Classification: G02B,G03H,G11B

Abstract:
1. A diffraction element comprising: a light-transmittable member; and a diffraction grating which is formed on at least one face of the light-transmittable member; wherein when a first laser beam having a first wavelength λ1 and a second laser beam having a second wavelength λ2 are transmitted through the diffraction element, the diffraction element turns the first and second laser beams into first and second diffracted beams having first and second diffraction efficiencies, respectively; wherein the diffraction element functions to equalize the first and second diffraction efficiencies by only the one face of the diffraction element; and wherein the diffraction grating has a first phase modulation amount ø1 for the first laser beam and a second phase modulation amount ø2 for the second laser beam and the first and second phase modulation amounts ø1 and ø2 are, respectively, approximately expressed by the following equations (1) and (2): in which “N1” and “N2” are natural numbers and “Δø” is a phase variation amount.