High-quality Brewster's angle polarizer for broadband infrared application

We have designed and constructed a linear polarizer for use with visible and infrared radiation. The broadband polarizer consists of four germanium plates arranged In st chevron geometry. Input radiation is incident near Brewster's angle for the first plate such that the reflected beam is preferentially s-wave polarized. This reflected beam is steered subsequently to the successive plates, always intersecting near Brewster's angle. The beam polarization at the output of the device is almost completely s-wave polarized. The ratio of the the paraxial flux of the nearly extinguished p-wave polarized light to the s-wave polarized light transmitted through the device is found to be less than 10(-5) for laser illumination at wavelengths af 0.638, 1.32, 3.39, and 10.6 mu m. Calculations predict that extinction ratios less than 10(-5) are achievable over the wavelength range from 0.4 mu m to beyond 500 mu m. Alternative design geometries involving fewer plates are also described along with their advantages and disadvantages.