Fabrication of optical waveguides by indiffusion of metals

A method of fabricating a light guide along a surface of a crystal transparent to at least a portion of the optical spectrum comprising the steps of providing a path of increased index of refraction along said surface, said path forming a light guide;

• and providing means for coupling an optical wave into said light guide;
• characterized in that said step of providing a path of increased index includes the step of depositing a layer of a diffusant selected from the group consisting of elements having atomic numbers 21-30, gold and silver onto said surface of said crystal, said layer having a thickness in the range of about 200 Angstroms to about 800 Angstroms and indiffusing said diffusant by heating said crystal to a temperature in the range of about 800 degrees C. to 1100 degrees C. for a time between four hours and eight hours, said time being sufficient to effect an increase in the index of refraction of a surface layer of said crystal suitable for guiding an optical wave, said increase being of the order of one percent at said surface and which decreases by one-half at a depth of the order of one micrometer below said surface.