Low-Loss Ultra-Compact Silicon Photonic Integrated Micro-Disk Modulator for Large-Scale WDM Optical Interconnection

Silicon-based wavelength-division-multiplexing (WDM) optical interconnection networks have recently been emerged as an effective solution in the datacenter to cope with the ever-increasing data traffic thanks to high data throughput and low power consumption. In a WDM network, a high-speed electro-optic modulator is a key component that encodes the signal to be transmitted on an optical carrier. However, the conventional modulators usually have a large size and relatively high power-consumption. For future high-density and large-scale integrated photonic circuits, small footprint and low power-consumption is significantly preferred. In this paper, we propose and design a low-loss ultra-compact silicon photonic micro-disk modulator (MDM). The proposed MDM has a specifically-designed slab waveguide to make the disk waveguide compatible with the lateral PN junction, which enables the MDM fabrication directly using the standard foundry multi-project wafer (MPW) run. An ultra-compact MDM with a radius as small as 3.7 μm is designed, fabricated and characterized. Its off-resonance insertion loss is measured to be less than 0.7 dB, and its measured electro-optic frequency response shows a modulation bandwidth as broad as 30.5 GHz. The performance of using the MDM to perform modulation of a 25 Gbit/s nonreturn-to-zero 2⁹-1 pseudorandom binary sequence is also evaluated when the detuning wavelength is set to be 0.031 nm, corresponding to a modulation bandwidth of 14.5 GHz. The proposed MDM provides the above performance without altering a standard foundry MPW run and shares the advantages of MDM including ultra-compact footprint, low insertion loss, and wide modulation bandwidth, which can find extensive applications in large-scale WDM optical interconnection networks and microwave photonics.