Electrooptic guided-to-unguided mode converter

Experimental demonstration of electrooptic polarization conversion from a guided TE wave to an unguided TM wave in a thin-film light guide is reported. In the specific device we fabricated utilizing Ta
2
O
5
film and LiTaO
3
substrate, we have observed a 40-percent modulation when 500 V were applied across two electrodes spaced 50 μm apart. We present here a ray-optics analysis of the conversion process. With the inclusion of the Goos-Haenchen shifts, the analysis agrees well with the experiment.