Hybrid Photonic Crystal-Surface Plasmon Polariton Waveguiding System for On-Chip Sensing Applications

In this paper, a hybrid guiding system based on the low group velocity offered by photonic crystal (PhC) waveguides and vertical confinement as well as high field enhancement of surface plasmon polaritons (SPP) is proposed. We show that for efficient sensing, two-dimensional PhC waveguides with finite height require a high aspect ratio in the order of 30 in order to confine the guiding mode. Fabrication of devices with such a high aspect ratio is too challenging and inefficient for mass production. By combining a PhC waveguide and SPPs, the proposed system efficiently confines the optical mode vertically while benefiting from the lateral confinement enabled by PhC structures. As a result, the required aspect ratio drops to about 4, which makes the fabrication feasible. This design provides strong light-matter interaction within small dimensions which is beneficial for miniaturizing on-chip photonic sensors.