A 1.23pJ/b 2.5Gb/s monolithically integrated optical carrier-injection ring modulator and all-digital driver circuit in commercial 45nm SOI

Integrated photonic interconnect technology presents a disruptive alternative to electrical I/O for many VLSI applications. Superior bandwidth-density and energy-efficient operation can be realized through dense wavelength-division multiplexing (DWDM) and lower transmission losses. There are two main paths towards an integrated platform. Hybrid/heterogeneous designs [1-3] enable each component to be custom-tailored, but suffer from large packaging parasitics, increased manufacturing costs due to requisite process flows, and costly 3D integration or microbump packaging. Monolithic integration mitigates integration overheads, but has not penetrated deeply-scaled technologies due to necessary process customizations [4]. The first monolithic integration of photonic devices and electronic-photonic operation in sub-100 nm (45 nm SOI process with zero foundry changes) is demonstrated in [5]. This paper presents a monolithically integrated optical modulator with a new all-digital driver circuit in a commercial 45nm SOI process. The waveform-conditioning driver circuit enables the carrier-injection modulator to operate at 2.5Gb/s with an energy-cost of 1.23pJ/b, making it ~4× faster and more energy-efficient than the previous monolithically integrated driver/modulator presented in [5].