We provide an elaborate investigation on the role of a hybrid wave (HW) in electromagnetic enhancement by a groove doublet in metallic substrate. A simple HW model is built to explore the detailed effect of HW on electromagnetic enhancement. The effective range of electromagnetic enhancement is obtained within 0.1λ away from a metal surface. The excitation of HW by a single groove has a gentle growth (from 0.03 to 0.26) as the groove gets wide, which implies that the emerging field of HW launched by a single groove is quite weak for narrow ones. HW, being like an “energy porter,” takes away partial energy from the Fabry–Perot resonance, which will be further coupled into the fundamental mode in the other groove after traveling along the metal surface. Our analysis reveals a compensation of electromagnetic enhancement for wide grooves attributed to the appearance of HW. The dependence of HW and electromagnetic enhancement on the noble metal type is also discussed.
© 2014 Optical Society of AmericaPDF Article