A Theoretical Study on an Optical Switch Using Interfered Evanescent Light
In an optical configuration consisting of a flat plate of vacuum between upper and lower spaces of uniform dielectric regions of n>1, we have calculated two output light intensities for two input lights from the Maxwell's equations as functions of the incision angle, a light intensity ratio, a phase difference of the two input lights, and a thickness of the vacuum layer, where the two input lights come from upper and lower dielectric regions with the same incision angles, and one of the output light goes into upper dielectric and the other goes into lower dielectric. We have found that, when evanescent lights exist at the upper and lower boundary and interfere each other, there is one set of incision angles and phase differences for any combination of an input light ratio and a thickness of the vacuum layer where one of output lights becomes zero. This finding will possibly lead to an innovative optical switch with which an optical output light can be switched on and off with a control light with an intensity much lower than that of the output light.