Novel three-dimensional 90° bend waveguides with high optical transmission efficiency based on silicon-on-insulator

Bend waveguide is an indispensable device in photonics integrated circuits (PICs). In this work, we propose and design two novel 3D 90 degrees bend waveguides based on the silicon platform with asymmetrically semicircular and trapezoidal cross-sections. Strip bend waveguides with bending radii of 10/20 mu m and cross-sectional size of 4 x 3.5/5 x 3.5 mu m2 are used for comparison. The high optical transmission efficiency of the two novel 3D bend waveguides is validated by simulated data. The bent structures are manufactured on the device layer of silicon -on-insulator (SOI) using 3D grayscale lithography. The fiber-to-chip measured results indicate that at 1550 nm and TE/TM mode, the transmission efficiencies of the asymmetrically semicircular and trapezoidal bend waveguides with bending radii of 20 mu m and cross-sectional widths of 4 mu m are 1.91/1.66 dB and 1.36/1.15 dB higher than those of the strip bend waveguides. When the cross-sectional width is 5 mu m, the two novel 3D bend waveguides are 1.99/1.72 dB and 1.46/0.98 dB higher than those of the strip bend waveguides. The 3D bend waveguides can effectively reduce the insertion loss. This research suits for the realization of highly integrated photonics computing chips.