| The use of optical nano-antennas to circumvent the diffraction limit by amplifying the light signal has been a main principle of nano-plasmonics. This thesis exploits the idea of optical antennas by introducing the bowtie and bowtie aperture structures to enhance the electric field of an incident signal. Due to the analogy of controlling electromagnetic waves with classical antennas, the thesis first provides reviews and theoretical descriptions of classical antennas. We then design and analyze bowtie and bowtie aperture antennas at microwave. In the second half of the thesis, we examine the important optical phenomena that accompanies with surface plasmons and surface plasmon polaritons in a metal-dielectric interface. By using the finite element method, we implement and characterize the bowtie and bowtie aperture optical antennas by gap dependence, structure dimensions, and oblique incidence. As a result, bowtie and bowtie aperture optical antennas enhanced high electric field in the gap at near-infrared and optical frequency regions. Moreover, a new approach that can clearly explain the behavior of light scattering of molecules near nano-antennas was studied. For optical antennas, near field interactions were analytically investigated by employing a Hertzian dipole wave excitation and the dyadic Green's function. We finally computed the enhancement factor and polarizabiltiy when the critical condition is most nearly satisfied. |
