Fabrication of wire-grid polarizers and dependence of submillimeter-wave optical performance on pitch uniformity

We describe a device for fabricating high-precision free-standing grids of fine wire, suitable for use as polarizing elements for radiation at millimeter and submillimeter wavelengths. Computer control of the winding process makes changing grid parameters particularly convenient and flexible. We present measurements of the mechanical uniformity and of the optical performance of wire grid polarizers made with 25 m and 10 m diameter wire. The flexibility of computer control is exploited to introduce a known degree of randomness in the grid pitch (center-to-center wire spacing), allowing the dependence of polarizer quality on uniformity to be quantified. This information allows prediction of the fabrication tolerances required for polarizers to be used at very high frequencies.