A Voyage from Plasmonic to Hybrid Waveguide Refractive Index Sensors Based on Wavelength Interrogation Technique: a Review

This study describes the underpinning theories and principles in the field of surface plasmon polariton generation and waveguide construction, as well as many design structures based on these waveguides that generate diverse optical resonances and their use for sensing refractive index and temperature variation. Firstly, the investigation of the topologies of plasmonics refractive index sensors based on Bragg grating structures and resonators (cavity and ring) that are coupled to the main bus waveguide is done. Secondly, these architectures’ theories and analytical frameworks are summarized. Following that, contemporary sensor development trends based on metal–insulator–metal–resonators (ring or cavity) architecture have been discussed. They have also been compared in terms of performance measures like sensitivity and figure of merit. The results of the comparison demonstrated that sensitivity can be greatly improved, but the figure of merit and quality factor still need to be improved in plasmonic-based sensors. Finally, some recent instances of hybrid plasmonic waveguides connected to a ring resonator have been manifested, which significantly improve the figure of merit and quality factor as compared to plasmonic waveguide–based sensors. Moreover, such structures are easily fabricated due to their CMOS compatibility.