Small fast large-aperture light modulator using attenuated total reflection.

An optical modulator is described which offers several advantages in terms of speed, aperture size, and ease of operation over other techniques for amplitude modulation of a collimated light beam. This simple device consists of a prism separated from a metallically reflecting surface by a small micron-size gap. Varying the gap thickness changes the intensity of the light reflected off the base of the prism. The prism acts as a coupler for the excitation of surface plasmons on the metallic surface. This paper explains the principle of operation and presents experimental results obtained on a simple realization of the device.