Abstract

Optical switching in thermooptical Si etalons has been demonstrated. In initial experiments a pulsed CO₂ laser beam is used to heat a Si etalon and shift the interference fringe of a 1.1- and 1.5-μm probe beam. It is shown that the switching time can be greatly reduced from ms to μs by choosing a probe beam of shorter wavelength in an external switching configuration. The switching time has further been improved to the ns range by the use of a 1.06-μm Nd:YAG laser pump which is presumed to give rise to a thermorefractive change in the Si etalon; at the same time, the switching threshold energy has been reduced to ~1 μJ compared with ~1 mJ for a CO₂ laser pump. Different etalons with thicknesses of 400 μm, 72 μm, and 1.5 μm have been examined to optimize the switching characteristics. We find that the 72-μm etalon exhibits the best behavior in terms of low power threshold, high speed, and contrast. In addition, the pump power dependence of the signal pulse shape has been investigated which indicates a multiple interference fringe shift and transverse thermal relaxation dynamics. Finally, by aligning one etalon at switch-on and another at switch-off, we demonstrate a write and erase optical logic system.

© 1991 Optical Society of America