A low-cost wire grid polarizer with an average extinction ratio of 40 dB in SWIR range realized by oblique angled deposition

Classical metal wire grid polarizers are commonly employed as infrared polarizers due to their broad operating spectrum. However, their low extinction ratio limits applications in high-precision infrared polarization in short-wavelength infrared range. Analysis using the Rigorous Coupled Wave Analysis indicates that the extinction ratio of a metal wire grid polarizer is positively correlated with the depth of the metal grating layer. Traditional etching and lift-off methods are insufficient for achieving the necessary depth to realize a high extinction ratio. In this paper, we propose an approach to fabricate infrared wire grid polarizers with ultra-high extinction ratios by combining Laser Interference Lithography with Oblique Angled Deposition method. The wire grid polarizer has a periodic structure of 300 nm and a grating layer depth of 450 nm, with an aspect ratio of 3:1. Experimental results demonstrate that the average transmission for TM wave exceeds 70 %, while the average extinction ratio surpasses 40 dB (10000:1) within the 1 μm to 2.5 μm range. The wire grid polarizer fabricated using the simple and low-cost methods has the potential to become a commercially viable product.