Interaction of two guided-mode resonances in an all-dielectric photonic crystal for uniform SERS

For sensing and imaging applications of surface-enhanced Raman scattering (SERS), one needs a substrate with the capability of generating a consistent and uniform response and increased signal enhancement. To this goal, we propose a photonic-crystal (PC) structure capable of supporting large field enhancement due to its high quality-factor resonance. Moreover, we demonstrate that the interaction of two modes of this all-dielectric PC can provide an almost uniform field enhancement across the unit cell of the PC. This is of practical importance for SERS applications. The designed structure can support a maximum field enhancement of 70 and 97 percent of uniformity.