Out-of-Plane Symmetry-Protected Bound States in the Continuum in a Plasmonic Nanofin Metasurface

We present a plasmonic nanofin metasurface harnessing the out-of-plane symmetry breaking in parameter space by tuning the triangle angle of 3D laser nanoprinted polymer triangles (named as nanofins) coated with gold. The plasmonic nature of the out-of-plane symmetry-protected BICs enables high field enhancement together with high q-factors from the near- to mid-infrared regions, which were utilised for refractive index and pixelated molecular sensing.