Nanophotonic Ring Resonator Based on Slotted Hybrid Plasmonic Waveguide for Biochemical Sensing

Abstract

Hybrid plasmonic waveguide (HPW) holds great promise as a potential nanophotonic platform for a variety of applications including biosensing which usually requires strong analyte–matter interaction. We propose a nanophotonic ring resonator based on a slotted HPW (SHPW) as a platform to realize resonance-enhanced sensing with strong light–analyte interaction on a subwavelength scale. The optical mode guided in the bus waveguide gets coupled to the slotted ring as a hybrid plasmonic (HP) mode which enables efficient bio-sensing. The SHPW utilized in the ring provides a larger propagation length of over 2.5 mm with subwavelength confinement at the wavelength of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.55 \mu \text{m}$ </tex-math></inline-formula> . The slotted structure also exhibits broadband propagation of HP where the propagation length remains around 1.2 mm over a wavelength range from 1.3 to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.6 \mu \text{m}$ </tex-math></inline-formula> . A 29.6-nm shift in the transmission spectra of the engineered ring resonator is observed on changing the analyte refractive index to 1.3514 (polluted water) from 1.333 (pure water). The sensitivity for the detection of polluted water is reported to be 1609 nm/RIU, which is approximately four times more than the dielectric slotted ring resonator and eight times more than the ring resonator with a ridge structure. The proposed engineered slotted waveguide structure may be helpful in realizing nanophotonic devices for various applications, including biochemical sensing and large-scale photonic integration.