Patent ID: 8254028
Filing Date: 2012-08-28
Classification: G02B,Y10T

Abstract:
1. A diffraction grating structure comprising: a substrate having a first surface and a second surface opposite to the first surface, wherein a first grating is defined on the first surface and a second grating is defined on the second surface, the first grating includes a plurality of first grooves and has a first grating period d 1 , and the second grating includes a plurality of second grooves and has a second grating period d 2 , and wherein the profile of the first grooves of the first grating are described by the following function: and the profile of the second grooves of the second grating are described by the following function: where θ is a half of angle of two coherent beams radiating on the diffraction grating structure, tan θ represents the tangent of the angle θ, x1 is a longitudinal coordinate which has an origin at the centre of the first grating, and x2 is another longitudinal coordinate which has another origin at the centre of the second grating.