High sensitivity and ultra-compact liquid sensor based on a ring resonator with a CMOS-compatible hybrid plasmonic waveguide

In this work, an ultra-compact and high sensitivity ring resonator-based liquid sensor on a CMOS-compatible SOI platform, utilizing a horizontal slot hybrid plasmonic (HP) waveguide consists of the Cu plasmonic layer suspending above the Si channel waveguide as the sensing element, is proposed. Numerical results suggest that the waveguide sensitivity, 𝑆𝑤, of the proposed HP waveguide reaches as high as 0.84 with the propagation loss less than 0.06 dB/μm, showing a similar Sw and a lower propagation loss in comparison to the typical plasmonic waveguide. In addition, with the scenario of SOI photonic platform continuously standardizing with the established CMOS methodologies for taking the advantages of the CMOS technology, the proposed miniaturized liquid sensor employing the Cu plasmonic element indicates the potential for the monolithic electronic-photonic integration. The sensitivity of the proposed liquid sensor with a miniaturized radius of 2 μm is numerically demonstrated as 540.0 nm/RIU, which is approximately four times higher than that of the conventional Si ring resonator with the identical geometry. Meanwhile a larger FOM is also achieved in comparison to other reported HP ring sensors.