A practical V-shaped nano-aperture flanked with surface corrugations for beam focusing

A V-shaped nano-aperture flanked with surface corrugations at exit side for beam focusing is introduced in this paper. Our finite-difference time domain (FDTD) numerical algorithm results demonstrate that the V-shaped aperture with width at incident side d(2) as small as 10 nm and surrounded with 14 grooves with a constant depth of 80 nm can intensely excite a transmission and focusing the beam in far-field region. The beam propagating with 78.91 mu m focal length and similar to 4 mu m spot size can be obtained for the practical V-shaped nano-aperture which can be naturally formed during the FIB fine milling. Changing the groove number and aperture width at exit side d(1) has limited contribution on the transmission due to their nonlinear relations with the electric field intensity vertical bar E vertical bar.(2) The V-shaped nanostructures may be useful in nanophotonics devices.