| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for designing a diffractive optical element in which the diffraction efficiency can be improved even for a diffraction grating pattern having a complicated phase distribution where a plurality of diffraction gratings overlap each other. SOLUTION: In the method for designing a diffractive optical element 1 having branching and coupling functions between an optical fiber 2 and optical fibers 3, 4, first phase distribution by the interference between the optical fiber 2 and optical fiber 3 and second phase distribution by the interference between the optical fiber 2 and optical fiber 4 are converted into first and second sawtooth phase distributions, respectively. The first and second phase distributions converted into sawtooth patterns are superposed one or another, and the distribution with an equal or smaller phase or the distribution with an equal or larger phase is selected from the first and second phase distributions to form a synthesized phase distribution. The designed diffractive optical element has the above synthesized phase distribution on the diffraction grating plane. |
