Abstract
Abstract In this work, we use a designed optical antenna structure to analyze the frequency and polarization with varied antenna size and arrangement, respectively. First, we simulate the spectral response and near-field intensity distribution of single- and two-wire antenna using finite-difference time domain method. By modifying the antenna arrangement, such as the azimuth of long axis of the antenna, the gap width of two-wire antenna and the size of optical antenna, then we can have a better response to distinguish the different light. We illuminate the antenna array with different geometric condition at the same time. There is more powerful near-field optical signal nearby the structure when the frequency of incident light is corresponding to the resonance peak of spectrum. Considering the polarization of incident, when polarization is parallel to antenna’s long axis, the enhancement will be larger than the polarization perpendicular to antenna’s long axis, and then we can tell the difference of the wavelength and polarization of incoming light. We use electron beam lithography to design and fabricate gold nano-antenna array on the glass substrate. In the aspect of measurement, we utilize the collection mode near-field scanning optical microscope with total internal refection set-up to obtain the real near-field intensity distribution around the optical antenna by shearing force feedback.