We fabricated an infrared wire-grid polarizer that was made of a tungsten silicide (WSi) grating on a Si substrate. The photolithography by the use of the two-beam interference was conducted for generating the short-period grating structure. This photoresist pattern was used as a mask for the reactive ion etching of the WSi coating and the Si substrate. Consequently, we could fabricate the WSi/Si grating with 400-nm period and 550-nm depth that acted as a wire-grid polarizer. The transmittance of TM polarization was 58% at 4-μm wavelength, which exceeded the theoretical transmittance of Si (54%). This enhancement of the transmittance was caused by the reduction in the reflectance due to the subwavelength-grating structure. The extinction ratio at 2.7-μm wavelength was 20 dB. We also measured the extinction coefficient Îº of WSi, and verified that WSi was a suitable polarizing material in the mid-infrared range.© (2006) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.