Design and fabrication of sub-wavelength metal grating polarizer in visible broadband

In this paper, a sub-wavelength metal grating polarizer at visible region is designed by Finite Difference Time Domain (FDTD) method. We have analyzed the effects of the period, the thickness of metal layer and the duty cycle on the performance of the metal grating polarizer. Simulation results show that in order to increase the metal grating transmissivity and extinction ratio and to reduce the angle sensitivity (+/- 30 degrees), the period should be less than 200 nm; Therefore, the structure with 180nm period and an 120nm Al layer is chosen, and the transmission efficiency and extinction ratio is more than 75% and 25dB respectively. Finally, a prototype of the metal grating has been fabricated by holographic-immersion lithography and ion beam etching.