Design of high-efficiency, broad-bandwidth unpolarized transmission grating for femtosecond laser

摘要

An unpolarized fused silica transmission grating with 12501p/mm applying in femtosecond laser has been designed at 780nm center wavelength with 740nm~840nm bandwidth. By using the rigorous coupled-wave theory, computer optimization shows that: when the groove depth and duty cycle are about 1.51um～1.63um, 0.53～0.63 respectively, the first-order diffraction efficiency of a lossless-transmission surface-relief grating with a rectangular surface profile can reach to higher than 90% for total unpolarized wave under 28.2°±4°incident angle.