Spectral resonance of nanoscale bowtie apertures in visible wavelength

We report spectroscopic measurements of transmitted field through bowtie-shaped nanoscale apertures in visible wavelength region. Resonance in these apertures and its relation with the aperture geometry are investigated. The near-field spectral response is also investigated using finite difference time domain (FDTD) computation and compared with the spectroscopic measurements. The dependences of the peak wavelength and peak amplitude on the geometry of the bowtie aperture are illustrated. Design rules are proposed to optimize the bowtie aperture for producing a sub-wavelength, high transmission field. PACS 81.07.-b; 07.79.Fc; 71.36.+c; 78.66Bz; 42.79.Gn; 42.79.Vb