Near-field Enhancement by Guided Bloch Modes at the Second Stop Band of a Nonlocal Optical Metasurface

Nanoscale gaps in plasmonic dimers offer highly enhanced optical near-fields that can be used in optical sensing and detection. In this work, we show that the field in such gap hotspots can be further enhanced by combining the surface lattice resonances with Bloch modes at the second stop band of a nonlocal optical metasurface. This approach can be used to create efficient and reusable substrates for surface-enhanced Raman spectroscopy and other plasmonic sensors with cost-effective nanofabrication methods.