All-silicon carrier accumulation modulator based on a lateral metal-oxide-semiconductor capacitor

In silicon photonics, the carrier depletion scheme has been the most commonly used mechanism for demonstrat- ing high-speed electro-optic modulation. However, in terms of phase modulation efficiency, carrier- accumnlation-based devices potentially offer almost an order of carrier depletion. Previously reported accumulation modulator magnitude improvement over those based on designs only considered vertical metal-oxide- semiconductor （MOS） capacitors, which imposes serious restrictions on the design flexibility and integratability with other photonic components. In this work, for the first time to our knowledge, we report experimental demonstration of an all-silicon accumulation phase modulator based on a lateral MOS capacitor. Using a Mach-Zehnder interferometer modulator with a 500-μm-long phase shifter, we demonstrate high-speed modulation up to 25 Gbit/s with a modulation efficiency （V πLπ） of 1.53 V·cm.