Design Of Scanning Near-field Optical Probe Based On The Optical Nano-antenna

Nano-optical antennas efficiently couples the optical-frequency electromagnetic wave to sub-wavelength nano-photonic components, which was firstly brought out by the team coming from Stanford University, including K. B. Crozier in 2003. For the structure has strong enhancing and bunching effect and has the ability of collecting the energy of light efficiently into a limited region of subwavelength size. It significantly surpassed the limit of diffraction and realized the focus of light in nano-scale. which may be a way to processs the optical information and optical propagation in nano-scale and exhibit a tempting prospect in fields of Surpassing the micro imaging technology of high resolution , efficient detection of spectrum(Raman scattering. Auto-fluorescence ) , highly efficient solar cell, super-highly dense data store and nano- lithography . In this paper, we discuss the theory and method to design the resonant nano-antenna in near infrared band;and its influencing factor of field enhancement,we also research the design and the study of scanning near-field optical probe based on nano antenna which we discussed,which provide a new viable technology to increase the resolution of scanning near-field optical microscope (SNOM).We firstly present a method in theory to compute the nano-antenna and discuss the theory and method to design the resonant nano-antenna Combined with the Fabry-Perot resonant model ,and analyze that the field enhancement has something to do with the structure of nano-antenna, the direction of incident light , the polarization and the angle of incident light by using finite-difference time-domain(FDTD). The results show that the field enhancement changes with the structure of the antenna , the polarization and angle of incident light. In order to obtain the huge field enhancement , we should consider the direction and polarization of the incident light except the parameter of antenna. The field enhancement is largest when the polarization along the axis of antenna and the incident direction is perpendicular.In this paper we also research the design and the study of scanning near-field optical probe based on nano antenna which we discussed. A novel probe which is added a metallic dipole nano-antenna onto the tip of the ordinary probe is designed and discussed. When the sample light arrives at the nano-antenna, the huge field enhancement will be obtained at the antenna feedback for the surface plasmon resonances produced on the surface of the metal. The light coupled into the probe and the signal-to-noise ratio is increased, consequently the higher resolution is realized. The results show the new probe has higher sensitivity (about two magnitude orders) and contrast ratio, and the high resolution may be true.