Compact gate-all-around silicon light modulator for ultra high speed operation

In this paper, we propose a novel compact and ultra-high speed optical modulator, the performance of which is validated by 2D and 3D simulations. The light phase modulation is achieved by a gate-all-around (GAA) capacitive structure. The modulation efficiency and the speed of the proposed GAA structure are evaluated in accumulation and strong inversion operation modes. The good overlap between the optical mode and the modulated region together with capacitive operation provide one of the most efficient and fast modulations reported for sub-micron silicon device architectures. The effects of sub-micron scaling on both optical and electrical performances are critically analysed, together with the evaluation of the trade-off between optical loss and modulation speed for λ = 1.55 μm. Maximum frequencies of operation beyond 10 GHz are predicted by simulation for a cross section of 340 × 340 nm2 and micrometer modulator lengths. The modulation efficiency of VπL = 0.45 V cm, together with the speed and compactness make the GAA modulator ideally suited for on-chip optical signalling.