Electrically Controllable Wide Angle of View Optical Notch Filter.
DEPARTMENT OF THE NAVY WASHINGTON DC
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An electronically controllable, wide angle of view, notch filter operates to attenuate predeterminable narrow bandwidth wavelengths of light energy. An enclosure contains a selected material characterized by exhibiting strong quantum mechanical coupling between two determinable energy states of different levels above its ground energy state and also producing radiated emission within the desired narrow bandwidth wavelengths when externally excited to populate the upper of the two determinable energy states. Transparent windows at opposite ends complete the enclosure which is maintained at a desired temperature to vaporize the selected material. Two electrodes, oppositely positioned within the enclosure contiguous to its optical path, are connectable to a source of pulsed electrical energy to generate an electric discharge across the electrodes of sufficient strength to raise the vaporized selected material from its ground energy state to the lower of the two determinable higher energy states, causing selective absorption of predetermined narrow bandwidth wavelengths of light energy under the timed control of electrical actuation. Author