Compact and low-loss bent hollow waveguides with distributed Bragg reflector

In this study, a hollow bent waveguide with distributed Bragg reflectors (DBR) in silicon substrate was presented theoretically and experimentally. We used the two-dimensional finite-difference time-domain method to simulate bending transmission efficiencies for arc- and cut-type 90°-bent waveguides. The air core was embedded by Si₃N₄/SiO₂ multilayer. The multilayer stacks were deposited by using plasma-enhanced chemical vapor deposition on the top and bottom of air core. The lowest 90 degree bending loss is around 3.9dB for the arc-type bending waveguides and 0.8dB for cut-type bending waveguides, respectively. This waveguide demonstrates a possibility for higher density of integration in planar light wave circuits.