Abstract

In a parallel-coupled dual-racetrack modulator, resonant light in two resonators can interfere with each other. In lieu of critical coupling, such interference is capable of producing high extinction ratios (ERs) for high-speed modulation. Experiments demonstrate ERs of over 9 dB at 50 Gb/s and 40–50% modulation depth enhancement compared with a single-resonator modulator at 50–56 Gb/s with a peak-to-peak driving voltage of 2.3 V. Furthermore, joint modulation of two racetracks offers the possibility to combine two separate bits of driving signals to generate four-level pulse-amplitude modulation (PAM-4) without an external digital-to-analog converter (DAC). To tackle the complex multi-variable transfer function of this modulator, a procedure for configuring PAM-4 states is theoretically developed. Finally, we demonstrate 100 Gb/s PAM-4 with an electro-optic modulation power consumption of < 40 fJ/bit for this device.

© 2022 Optica Publishing Group

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