Fig. 1. Schematic configurations. (a) Top view of the TM-type CMWG. Zoom-in top view of (b) the grating corrugations and (c) the grating transition taper.

Fig. 2. (a) Simulated reflectivity and (b) the group delay spectrum for the case with different apodization length ratios η = 0, 10⁻³, 10⁻², and 10⁻¹. (c) Zoom-in group delay spectrum at 1542–1542.5 nm. (d) Average GDR variation as a function of modulated length ratio η.

Fig. 3. (a) Schematic configuration of period perturbation and (b) polygon misalignment. Simulated group delay spectrum with (black) and without (red) 0.1 nm period perturbation of (c) TE-type and (d) TM-type CMWGs. Simulated group delay spectrum with (black) and without (red) 2 nm polygon misalignment of (e) TE-type and (f) TM-type CMWGs.

Fig. 4. (a) Schematic configuration of the mode (de)multiplexer consisting of an adiabatic dual-core taper coupler. (b) Simulated light propagation in the designed adiabatic dual-core taper when operating at the wavelength of 1538 nm. (c) Simulated transmission spectrum for the dropped TM₀ mode in waveguide B (blue) and the residual TM₁ mode (red) in waveguide A.

Fig. 5. (a) Microscope images of the fabricated mode (de)multiplexer. (b) Measured multiplexer transmission spectrum for the TM₁ mode input for the dropped port and the through port.

Fig. 6. Microscope images of the fabricated CMWGs, including TM-type CMWGs with different lengths of (a) 5, (b) 15, and (c) 30 mm, respectively. Measured reflected transmission spectra for the TM-type CMWGs with different lengths of (d) 5, (e) 15, and (f) 30 mm, respectively.

Fig. 7. Measured group delay spectra of the fabricated spiral TM CMWGs with different lengths of 5, 15, and 30 mm.