Low-loss,high-index-contrast Si3N4/SiO2 optical waveguides for optical delay lines in microwave photonics signal processing

We report the design and characterization of si3n 4/sio2 optical waveguides which are specifically developed for optical delay lines in microwave photonics (mwp) signal processing applications. the waveguide structure consists of a stack of two si 3n4 stripes and sio2 as an intermediate layer. characterization of the waveguide propagation loss was performed in race track-shaped optical ring resonators (orrs) with a free-spectral range of 20 ghz and a bending radius varied from 50 μm to 125 μm. a waveguide propagation loss as low as 0.095 db/cm was measured in the orrs with bend radii ≤ 70 μm. using the waveguide technology two types of rf-modulated optical sideband filters with high sideband suppression and small transition band consisting of an mach-zehnder interferometer and orrs are also demonstrated. these results demonstrate the potential of the waveguide technology to be applied to construct compact on-chip mwp signal processors. © 2011 optical society of america.