Fig. 1. Modulator structure with a single-drive push-pull electrode

Fig. 2. Cross section of modulator with heteromorphic doped slot waveguide

Fig. 3. Normalized fundamental optical mode distribution in slot waveguide

Fig. 4. Carrier distribution on pn junction cross section at 0 V and 2 V. (a) 0 V; (b) 2 V

Fig. 5. Optical transmission loss and phase shift under different bias voltages. (a) Optical transmission loss; (b) phase shift

Fig. 6. Junction capacitance at different bias voltages

Fig. 7. T-shape electrode structure (W=50 μm, T=12 μm, d_gap=15 μm, P=90 μm) and equivalent circuit model of the loaded transmission line. (a) Electrode structure; (b) equivalent circuit model

Fig. 8. Simulated value of electrode equivalent circuit. (a) Capacitance per unit length; (b) inductance per unit length; (c) resistance per unit length; (d) loss per unit length

Fig. 9. Electrode impedance and refractive index with unloaded and loaded pn junction. (a) Impedance; (b) refractive index

Fig. 10. Electrode loss and 3 dB electro-optic bandwidth under different bias voltages. (a) Electrode loss; (b) electro-optic bandwidth

Fig. 11. Optical transmission spectra and modulation efficiency of 3 mm long modulator under different bias voltages. (a) Optical transmission spectra; (b) modulation efficiency

Fig. 12. 70 Gbit/s OOK modulation eye diagrams with V_pp=2 V. (a) Slot WG; (b) traditional rib WG