Fig. 1. Cross-sectional view of double-core rotator.

Fig. 2. Transmission spectra of double-core rotator. (a) Normalized by transmission of normal Si wire waveguide. (b) Normalized by transmission of a fiber.

Fig. 3. Calculated transmission spectra of the double-core rotator with various refractive indices of overcladding.

Fig. 4. Calculated bending loss of the Si waveguide with 400  nm×200  nm core for the bending radius of 5 μm as a function of the refractive index of overcladding.

Fig. 5. Cross-sectional view of the parallel-core rotator.

Fig. 6. Eigenmodes of the parallel-core structure.

Fig. 7. Schematic top view of the parallel-core rotator.

Fig. 8. Transmission spectra of the parallel-core rotator. (a) Normalized by transmission of normal Si wire waveguide. (b) Normalized by transmission of a fiber.

Fig. 9. Calculated transmittance of the parallel-core rotator with various spacer widths.

Fig. 10. Transmission spectra of the parallel-core rotator. (a) Spacer width, 50 nm. (b) Spacer width, 100 nm. (c) Spacer width, 150 nm.