Highly Efficient Broadband Optimization Design Of Gold-Plated Reflective Grating

Grating is a very useful diffraction optical element. Highly efficient and broadband gratings are required in current ultrafast femtosecond pulsed lasers. This paper mainly focused on gold-plated reflective gratings. We proposed a rectangular grating with high efficiency and broadband under Littrow incidence at the center wavelength of 800nm for TM polarization. Under Littrow incidence, the duty cycle and the groove depth of the grating determine the diffraction efficiency and bandwidth of the gratings. By the Rigorous Coupled Wave Analysis(RCWA) and simulated annealing algorithm, we analyzed the effects of different grating parameters on grating diffraction efficiency and bandwidth. In this paper, we designed a rectangular grating with duty cycle 0.324, groove depth 1466nm and thickness of connection layer 2146nm, respectively. Its diffraction efficiency of the -1 order approached 98% in broadband. And we analyzed the tolerance of our grating to improve the efficiency of the grating. This kind of grating has very important value in the future application of high power laser.