Multi-sided optical waveguide-fed photoconductive switches

Abstract

A photoconductive switch and optical transconductance varistor having a photoconductive region e.g. a wide bandgap semiconductor material substrate between opposing electrodes. An optical waveguide is arranged to surround the photoconductive region for directing conduction-inducing radiation into the photoconductive region. And an optical diffusion element is arranged to diffuse/disperse the radiation prior to entering the optical waveguide and into the substrate, for uniformly illuminating the substrate for conduction.

We claim: 
     
         1 . A photoconductive switch comprising:
 a wide bandgap semiconductor material substrate;   first and second electrodes in contact with said substrate;   an optical waveguide surrounding exposed facets of the substrate for directing conduction-inducing radiation into said exposed facets of the substrate; and   an optical diffusion element arranged to diffuse/disperse said radiation prior to entering the optical waveguide and into the substrate.   
     
     
         2 . The photoconductive switch of  claim 1 ,
 wherein the optical waveguide is coated with a reflective coating to reflect radiation into the exposed facets of the substrate.   
     
     
         3 . The photoconductive switch of  claim 2 ,
 wherein the optical diffusion element is a tapered light pipe connected to the optical waveguide.   
     
     
         4 . The photoconductive switch of  claim 1 ,
 wherein the first and second electrodes are in contact with said material so that a first triple junction boundary region is formed between the substrate and the first electrode and a second triple junction boundary region is formed between the substrate and the second electrode, and the substrate is located completely within a triple junction region formed between the first and second triple junction boundary regions.   
     
     
         5 . An optical transconductance varistor comprising:
 a wide bandgap semiconductor material substrate, whose conduction response to changes in amplitude of incident radiation that is substantially linear throughout a non-saturation region thereof, whereby the material is operable in non-avalanche mode as a variable resistor;   first and second electrodes in contact with said substrate;   an optical waveguide surrounding exposed facets of the substrate for directing conduction-inducing radiation into said exposed facets of the substrate; and   an optical diffusion element arranged to diffuse/disperse said radiation prior to entering the optical waveguide and into the substrate.   
     
     
         6 . The optical transconductance varistor of  claim 5 ,
 wherein the optical waveguide is coated with a reflective coating to reflect radiation into the exposed facets of the substrate.   
     
     
         7 . The optical transconductance varistor of  claim 6 ,
 wherein the optical diffusion element is a tapered light pipe connected to the optical waveguide.   
     
     
         8 . The optical transconductance varistor of  claim 5 ,
 wherein the first and second electrodes are in contact with said material so that a first triple junction boundary region is formed between the substrate and the first electrode and a second triple junction boundary region is formed between the substrate and the second electrode, and the substrate is located completely within a triple junction region formed between the first and second triple junction boundary regions.   
     
     
         9 . A photoconductive switch comprising:
 a wide bandgap semiconductor material substrate;   first and second electrodes in contact with said substrate and defining a triple junction region therebetween, with all remaining surfaces of the substrate having a reflective coating to internally reflect conduction-inducing radiation; and   an optical diffusion element arranged to diffuse/disperse said conduction-inducing radiation into the substrate so that the triple junction region may be uniformly illumated and made conductive.   
     
     
         10 . The photoconductive switch of  claim 9 ,
 wherein the optical diffusion element is a tapered light pipe connected to a face of the substrate.