Metal–Dielectric Composite Nanostructures for Fano Resonance-Based Highly Sensitive SECARS from Visible to Deep-UV

Abstract

The nanostructures of noble metals are known to support Fano resonances, in most cases, in the infrared. Blue-shifting Fano-resonant spectral range is of great importance for practical applications. Here, we propose to use metal–dielectric composite nanostructures for this purpose. In the nanostructures containing noble metal nanoparticles with moderate sizes, Fano resonances appear in the visible because of the composite effect. By changing the host medium and the filling factor of metal nanoparticles in the composite nanostructures, Fano-resonant spectral region can be tuned in a wide range. These composite nanostructures exhibit field enhancement significantly high that they are applicable for a single-molecule detection based on surface-enhanced coherent anti-Stokes Raman spectroscopy (SECARS). In particular, the dielectric composite nanostructures containing Mg and Al nanoparticles support Fano resonances, providing unprecedentedly high SECARS enhancement factors in the near- and deep-ultraviolet reg...