Ultra-compact, low-loss,TE0- and TE1-compatible mode waveguide bends

Abstract

Waveguide bends have become an interesting research direction because they allow highly curved light transmission in a limited space. Here, we propose waveguide bends supporting two TE modes by etching slots and adding germanium arcs in the inner side of a waveguide bend. Simulations show that the bending radius of our proposed base-mode TE0 waveguide bend drops to 500 nm and its insertion loss (IL) is reduced to 0.13 dB with footprints as small as 0.75µm×0.75µm. For the higher-order TE1 mode waveguide bend, we adjust the introduced structure in combination with the light field distribution. The IL of the waveguide bend is also reduced to 0.18 dB with footprints as small as 1.85µm×1.85µm. TE0 mode has 410 nm bandwidth in the optical communication band while TE1 mode has 330 nm bandwidth by keeping IL<0.5dB. Through the analysis of these structural characteristics, we believe that this method still has great potential in higher-order mode transmission.