Effect of Metallic Nanoparticles on Improving the Detection Capacity of a Micro-SERS Sensor Created by the Hybrid Waveguide of Metallic Slots and Dielectric Strips

The enhancement factor (EF) of surface-enhanced Raman scattering (SERS) mainly depends on the electrical field intensity of surface plasmons in the place of Raman-active molecules. Because of this dependence, the Raman detection sensitivity is much higher with molecules in a small metallic gap than near a single metallic surface because of the intense local electric field resulting from the interaction between metallic objects. In this study, we investigate the SERS detection capacity improved by metallic nanoparticles in a micro-SERS sensor made of a metallic slot and a dielectric strip using the three-dimensional finite-difference time domain method. We calculated the field and charge distributions in the metallic sphere–slot junction to discuss the electromagnetic interaction between the in-sphere localized surface plasmon and the in-slot surface plasmon polariton. After that, the EF dependence of the sensor on the in-slot particle’s position, size, shape, and number is demonstrated and discussed to sh...