Catadioptric stark effect laser modulator for IFF interrogator - uses corner cube catadioptres and two sets of orthogonal plane mirrors forming rectangular section waveguide

摘要

The reflecting light modulator uses the Stark effect of field dependent absorption of a gas such as deuterated ammonia at low pressure, and is used to modulate laser generated light at wavelength between the far infra red and ultra violet. Monochromatic light is reflected parallel to its angle of incidence. The modulator consists of a metal chamber (1) with an optical window (2) filled with gas at low pressure. Absorption is controlled by varying the voltage applied to electrodes (31,35) in the cell. The reflecting element of the cell is an assembly of corner cubes (5) with their faces towards the window and an array of orthogonal plane mirrors (31,35) with metallic surfaces aligned perpendicular to the plane of the corner cubes and forming rectangular waveguides within the cell and serving as electrodes. The mirrors are alternately grounded or modulated. The electrodes do not provide obscuration and the field of view can be extended without minimising the depth of the cell. The field of view is limited to about 20 degrees by corner reflectors.