Light waveguide type polarized light beam splitter

Claim 1

A light waveguide type polarized light beam splitter comprising: a first region; a second region; and a boundary surface formed between said first region and said second region; wherein: said first region is a titanium diffused layer developed through diffusion of titanium into a lithium niobate substrate; said second region is a portion of the titanium diffused layer treated by a proton exchange process; said first region and said second region have differing refractive indices; said beam splitter is configured to pass an incident linearly polarized light beam, oscillating in a predetermined plane, propagating in a predetermined direction and entering the beam splitter via said second region, through said boundary surface, and is configured to reflect a return light beam, oscillating in a shifted plane of polarization, propagating in a return direction and entering the beam splitter via said first region, at said boundary surface; said boundary surface is inclined by an angle of θ 1 with respect to the direction of propagation of the linearly polarized light, and is inclined by an angle of θ 2 with respect to the direction of propagation of the return light beam; and the angle θ 2 is determined to satisfy the condition of °<θ.sub. ≦ cos.sup.-1 (n.sub.oP /n.sub.oT) wherein n oT represents a refractive index of the titanium diffused layer against ordinary rays, and n oP represents a refractive index of said second region treated by the proton exchange process against ordinary rays.