Fig. 1. (a) MZM schematic with proposed phase shifters. (b) Proposed phase shifter using heterogeneous strip-loaded waveguide.

Fig. 2. (a) Cross-sectional schematic of the proposed a-Si:H strip-loaded modulator. (b) Optical field of strip-loaded waveguide for 75 nm thick and 800 nm wide a-Si:H strip. (c) Cross-sectional schematic of a rib waveguide for conventional modulators. (d) Optical field of rib waveguide for 110 nm high and 600 nm wide rib.

Fig. 3. Confinement factors of strip-loaded waveguide and rib waveguide as functions of strip and rib height.

Fig. 4. Overlap integral of optical mode field and depletion region as function of strip and rib height.

Fig. 5. (a) Phase shift in relation to reverse bias. (b) PN overlap dependence of efficiency VπL.

Fig. 6. Comparison of propagation loss between the conventional lateral PN modulator in the rib waveguide and the proposed vertical one with three different overlap distances.

Fig. 7. Capacitance of the conventional lateral PN junction and the proposed vertical one as a function of bias.

Fig. 8. (a) Transient response and (b) frequency response of the proposed phase shifter.