▎ 摘　　要

A comparison between a graphene suspended double-layer modulator and a subwavelength-thickness modulator is presented. The physics of both are analyzed in detail and show a confined mode in the suspended modulator but a leaky mode in the subwavelength modulator. The leaky mode shows zero light-matter interaction and zero modulation depth, which should be avoided in designing a modulator. The suspended modulator can achieve much lower insertion loss and an extraordinarily higher figure of merit (similar to 2480) than the subwavelength modulator. Both operate with high modulation efficiency and comparable modulation speeds. We believe these designs will pave the way to realizing high-efficiency, near-fundamental-limit graphene modulators. (C) 2019 Optical Society of America