Compact Bends for Achieving Higher Integration Densities for LiNbO Waveguides

A new waveguide platform is demonstrated that allows the bend radii to be substantially decreased for titanium-diffused lithium-niobate (LiNbO 3 ) waveguides using vertically integrated arsenic-trisulfide (As 2 S 3 ) overlay waveguides. Power is transferred from a Ti-diffused waveguide into the overlay waveguide using tapers, guided by the As 2 S 3 waveguide through the S-bend region and transferred back into another Ti-diffused waveguide. This structure also behaves like a polarization beam splitter. We present simulation results as well as measurements to show the feasibility of achieving low loss and reduced bend radii for electrooptic waveguides.