Suspended graphene double-layer modulator with an ultrahigh figure of merit and a subwavelength-thickness modulator with leaky mode.

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 (∼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.