The Wire Grid as a Near-Infrared Polarizer

Wire grids have been fabricated with microscopic elements and periodicity. These wire grids behave as linear polarizers over large portions of the infrared spectrum, confirming predictions from electromagnetic theory. The method of fabrication of grids with periods as small as 463 mμ is described. Limits on the performance of a wire-grid polarizer are set by fineness of period, optical constants of the metal, spectral transmission of the supporting substrate, and by skin-depth effects. Within these limits, excellent polarizer performance may be obtained over a very wide band of wavelengths, and these new wire-grid polarizers do, in fact, cover the range 2–15 μ and beyond. Appreciable polarization is observed at near-infrared and visible wavelengths. Wire grids may be used in convergent beams of radiation or in restricted geometrical arrangements, unlike many pile-of-plate or prism polarizers. These wire-grid polarizers have proved useful in measuring the imperfections of other types of infrared polarizers.