A Sub- $\lambda$ -Size Modulator Beyond the Efficiency-Loss Limit

Electrooptic modulators (EOMs) are key devices in performing the conversion between the electrical and optical domains in data communication links. With respect to a road map for photonic computing, future EOMs are required to be highly scalable, should feature strong modulation performance, and must not consume much power during operation. In light of these requirements, here, we investigate indium-tin-oxide (ITO) as an electrooptic switching material. The results show that ITO is capable of changing its extinction coefficient by a factor of 136. Utilizing these findings, we analyze an ultracompact (i.e., sub- λ long λ = 1310 nm) electroabsorption modulator based on a plasmonic MOS-mode design. In our analysis, we investigate the performance, i.e., the extinction ratio and insertion loss of the device as a function of various geometric parameters of the device. The optimized device is 0.78 λ long and features an extinction ratio and on-chip insertion loss of about 6 dB/μm and 0.7 dB, respectively. Furthermore, we suggest a metric to benchmark electroabsorption modulators and show that silicon plasmonics has potential for high-end switching nodes in future integrated photonic circuits.