Lineshape measurement for coupling to waveguide modes in the prism-film coupler

Coupling to optical waveguide modes was investigated by depositing two thin film layers on the hypotenuse of a rutile prism. Coupling efficiency was determined as a function of input beam angle for the three lowest order TE and TM modes. The coupling lineshape was found to agree with the predictions of a lossless, ray-optics analysis for all but the lowest order TM modes. This result is explained in terms of the relative effects of loss on the coupling efficiencies of the various modes.