Plasmonic Absorber Based on Engineered Cu-ITO Structure on Silicon With Low Voltage Tuning and High Extinction Ratio

An electrically tunable plasmonic absorber device is experimentally demonstrated at 1550 nm wavelength. The device consists of alternating Cu- ITO grating on the top of a p-type silicon rib waveguide, filled with n-type indium tin oxide (ITO) as a capping layer. The distributed plasmonic mode at the interface of Cu-SiO
₂
-Si is efficiently coupled with ITO. The electrically tunable permittivity of ITO changes the optical absorption by employing electrically driven carrier depletion and accumulation. We demonstrate large tuning of optical intensity by electrically driven carrier accumulation at ITO interface by applying very low voltage from 0 to −4 V. A 100-μm long device exhibits a high extinction ratio of 22 dB and wide 3 dB bandwidth of 52.2 GHz. Applications for our proposed device include imaging, biosensing, intensity modulators, and other multi-functional nanophotonic devices where change in optical absorption is a key requirement.