Low loss optical waveguides and polarization splitters with oxidized AlxGa1-xAs layers
Low propagation loss waveguides, operating at 1.55 fim optical wavelength, are fabricated utilizing oxidized AhGai_a;As layers. MBE grown multilayer semiconductor heterostructures are characterized before and after oxidation by ellipsometric techniques. In fabrication of optical waveguides, reactive ion etching method is used extensively. Loss measurements are performed, involving a fiber input-coupled laser source setup using Fabry-Perot resonance technique. Propagation loss of an AlGaAs based multilayer rib waveguide with oxidized AhG ai_3,As top layer is observed to reduce from 6 dB/cm to as low as 1 clB/cm lor TM and from 3.7 dB/cm to as low as 0.6 dB/cm for TE polarizations in the presence of metal electrodes on top of the rib. These results arc compared with loss measurements on standard rib waveguides. Polarization splitters are also fabricated with the same material. Effect of the oxide layer on the polarization splitter’s coupling length for TE and TM polarizations are measured. Polarization extinction ratios as high as 12.4 dB are obtained. Polarization extinction ratios are also attempted to be controlled by the use of electro-optic effect in Al.x,.Gai_a;As system. Only AC fields are found to be effective.