Design of Compact, Broadband, and Low-Loss Silicon Waveguide Bends with Radius under 500 nm

Abstract

Waveguide bend is an indispensable component in the on-chip compact photonic integrated circuits (PICs) and the minimum bend size greatly limits the increase of integration density of PICs. Here, we propose broadband and low-loss silicon waveguide bend schemes using air trenches on both sides and embedded germanium arc in the inner side of waveguide bend. Using these ways, the silicon waveguide bending radius can be greatly reduced to less than 500 nm and the obtained insertion loss (IL) can be as low as 0.12 dB compared with IL = 1.73 dB obtained by direct silicon waveguide bend under the same bending radius. Meanwhile, the working bandwidth can be extended over 500 nm covering the whole optical communication band by keeping IL < 0.5 dB. Therefore, the proposed device schemes could push the development of on-chip PICs toward higher integration density.

Ultra-compact and efficient photonic waveguide bends with different configurations designed by topology optimization

“…Despite the capability of high optical confinement in a silicon waveguide, the bends are still prone to significant propagation loss, particularly as smaller bend radii are employed 5 . The loss of optical mode in a bend waveguide is attributed to three main reasons (i) loss due to non-zero curvature of the waveguide (ii) mode mismatch between the input and output waveguide, and (iii) loss due to scattering and absorption in the waveguide 6 .…”