Electric field enhancing properties of the V-shaped optical resonant antennas

The electric field enhancing properties of the V-shaped optical resonant antenna are studied by using finite-difference time-domain method. Both dipolar and quadrupolar modes can be effectively excited and strong electric field enhancement in the gap of the V-shaped antenna is found. Compared with full-wave dipole antenna, the V-shaped antenna has a greater electric field enhancement, which can be attributed to the higher radiation directivity and the smaller curvature radius of the antenna arms. The more asymmetrical structure also contributes to the efficient quadrupolar excitation. The electric field enhancement of the V-shaped antenna has different dependences on the open angle of the V-shaped antenna for the dipolar and quadrupolar excitation. We obtained stronger electric field enhancing properties by using V-shaped bow-tie antennas, especially for the quadrupolar excitation. The V-shaped antenna and the bow-tie antenna can realize strongly localized and enhanced field and thus are well suitable for the use of near-field optics applications. (c) 2007 Optical Society of America.