Parallel end-butt coupling for optical integrated circuits.

The method of parallel end-butt coupling has been used to couple GaAs laser diodes to Ta (2)O(5) thin film waveguides. Theoretical caluclations predict that a coupling efficiency into the lowest order waveguide mode of 90% is achievable if the thicknesses of the waveguide (t(g)) and the laser light emitting layer (t(L)) are equal. Experimentally, efficiencies as high as 45.1% have been measured for laser and waveguide combinations with t(g)/t(L) = 0.34. The tolerance to misalignment of the laser and waveguide has been theoretically and experimentally evaluated.