Patent ID: 7410286

Claim:
A tapered-waveguide optical apparatus including: an input waveguide in the form of a slab, the input waveguide comprising a first input end for injection of light such that it bounces along the input waveguide and travels to a first output end; and an output waveguide having two opposed main faces and a second input end for receiving light at various angles of incidence from the input waveguide, wherein the output waveguide is arranged to allow light to propagate a certain distance by reflection within the output waveguide at successively steeper angles of incidence on said opposed main faces and then to emit the light over one of the faces of the output waveguide when the angle of incidence at that one face exceeds the critical angle for total internal reflection; in which the output waveguide's thickness profile is such that the light of different angles of incidence at said second input end bounces the same number of times in total, on passing through the two waveguides, before leaving the output waveguide.