Bend Waveguides on Silicon Nanowire Optical Waveguide (SNOW)

In a previous work, we reported a novel optical waveguide named silicon nanowire optical waveguide (SNOW), which consists of arrayed silicon nanowires acting like an effective-index medium. In this paper, we analyze bend properties of the waveguide and show that small radii bends can be achieved in SNOW structures with low radiation losses. For bend radii of 5 and 2 μm at a wavelength of 1550 nm, the radiation loss per 360° turn is 5 ×10^-4 and 0.05 dB, respectively. Furthermore, we study the losses for changing the pitch between the nanowires and show that the loss behavior follows effective-index bulk waveguide approximation. Consequently, we show that the bending losses can be optimized by arranging the nanowires pitch size such that the density is higher in the inner side of the bend as compared with the outer side. Effects of wavelength and sidewall roughness on propagation loss are also investigated.