Asymmetric waveguide devices with buried AlOx cladding layers

We demonstrate a highly asymmetric waveguide filter for wavelength division multiplexing applications using wet oxidation of AlAs to form low-index cladding layers. The dual waveguide structure consists of a low-index polymer waveguide coupled to a lossy high-index AlGaAs waveguide. The high asymmetry between the polymer and AlGaAs yields high resolution at small device lengths. The light is coupled in and out of the polymer guide and exhibits Fabry-Perot-like resonances as the light couples to different modes of the AlGaAs. With a device length of 400 μm, we observe resonances with a width of about 1 nm at 800 nm, agreeing with theoretical expectations. In addition to the simple filter demonstrated here, such a structure could be used to form active light emitting or detector devices.