Ultralow-bending-loss surface-plasmon-polariton waveguides

We report the transmission, reflection and loss properties of 90-degree and 135-degree bent silicon waveguide and 90-degree and 135-degree bent surface-plasmon polariton (SPP) waveguides composed of metal thin film and silicon. Finite difference time domain simulation analysis shows that the maximum bending transmittances of 90-degree bent and 135-degree bent silicon waveguides are 51% and smaller than 10%, respectively, and the maximum bending transmittances of 90-degree bent and 135-degree bent SPP waveguides are 80% or so, and they are higher 30% and 70% than that of identically-bent silicon waveguides, respectively. Moreover, the SPP waveguide bend with metal thin film as inner layer of the bend and silicon as outer layer of the bend has much higher transmission than ones with silicon as the inner layer and metal thin film as the outer layer. The waveguide bend with metal as the inner layer and dielectric as the outer layer will be potential for integrated photonic devices and subsystem.