Fig. 1. High-speed modulator structure. (a) Planar view; (b) transverse section view

Fig. 2. Distributions of optical field and carrier concentration in waveguides of various widths (300, 400, 500, 600 nm) under applied voltage of 3 V. (a) Optical field distribution; (b) carrier distribution

Fig. 3. Impact of doping concentration on modulator performance. (a) Modulation efficiency; (b) loss

Fig. 4. Simulation model of traveling wave electrodes in HFSS. (a) Simplified traveling wave electrode model; (b) simulation modeling in HFSS

Fig. 5. Traveling wave electrode differential impedance parametric sweep

Fig. 6. 2.5 mm-long modulator. (a) Illustration of segmental MZM model; (b) equivalent 100 μm model in ADS; (c) 2.5 mm model

Fig. 7. Bandwidth simulation curve

Fig. 8. Transmission spectrum of a single-ended push-pull modulator

Fig. 9. Half-wave voltage test

Fig. 10. Modulator S-parameters test results. (a) S₂₁; (b) S₁₁

Fig. 11. Modulator eye diagram test results. (a) 20 Gbit/s; (b) 40 Gbit/s; (c) 56 Gbit/s

Fig. 12. Block diagram of system-level testing for I/Q modulator

Fig. 13. QPSK packaged modulator constellation diagram and eye diagram test results. (a) I、Q single-channel test; (b)‒(f) 10、20、30、40、50 Gbit/s constellation diagram and eye diagram test results of QPSK packaged modulator

Fig. 14. Modulator fabrication process variations. (a) Gap is 24.89 μm, W is 26.66 μm; (b) Gap is 25.10 μm, W is 26.53 μm; (c) Gap is 24.73 μm, W is 26.89 μm; (d) Gap is 24.94 μm, W is 26.89 μm; (e) Gap is 24.86 μm, W is 26.81 μm; (f) Gap is 24.74 μm, W is 26.85 μm