Localized field enhancements in two-dimensional V-groove metal arrays

We investigate field enhancements in two-dimensional 800 nm periodic arrays of (108–121 nm deep) V-grooves (opening angles 38°–75°) fabricated using focused ion beam milling in a 190 nm thick gold film on top of a fused silica substrate. Simulated and experimental reflection spectra, high-resolution two-photon luminescence (TPL) images, and microscopy of surface-enhanced Raman scattering (SERS) obtained from the V-groove metal arrays are compared and reveal good correspondence in the spectral dependences of reflection and local TPL as well as SERS measured at the groove bottom. We relate the obtained field intensity enhancements, reaching ∼85 with nanofocusing and resonant interference of counterpropagating plasmons by the periodic closed tapered groove gaps. The achieved reflection spectra and enhancements depend on the geometry of the V-groove arrays and can actually be tuned in the wavelength range from visible to infrared, making this configuration promising for a wide range of practical applications, e.g., within surface-enhanced spectroscopies.