be reflected to the port 46 if the input intensity is large then the index of refraction n 1 i also becomes large and the critical angle u03b8 c u03b8 c high becomes small if u03b8 c high is smaller than u03b8 1 then the light will experience total internal reflection and will be passed down to the output port 46 at the angle of reflection u03b8 r as shown the selection of the angle of incidence u03b8 1 is critical for operation of the inverter 20 particularly u03b8 1 must be such that it is greater than the critical angle u03b8 c for a high intensity input but less than the critical angle u03b8 c for a low intensity input that is u03b8 c high lt u03b8 1 lt u03b8 c low the inverter 20 operates as follows the optical digital beam is combined with the output of the laser 26 the resulting optical signal is composed of pulses having high and low levels which are level shifted versions of the digital input beam this combined pulse beam enters the inverting switch 34 and sees a refractive index of n 1 i at a given time if the input pulse of the pulse beam is high the refractive index n 1 i of the structure 36.