Optical Nano-antenna And Its Application In Scanning Near-field Probe

Concept of nano-antenna 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 property of field enhancement of nano-antennas, the theory and method to design the resonant nano-antenna in near infrared band and its application in near-field optical probe.We firstly present the current situation and development of nano-antennas.then systematically analyze the relation of the field enhancement 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). Combined with the Fabry-Perot resonant model, we discuss how to design the optical nano-antennas and Obtain the graph between Phase Retardationφand incident wavelength as well as the ratio of monopole and dipole nano-antenna through repeated simulation.which can become a foundation to design the nano-antenna in near infrared band.In this paper we also research primarily the application of optical nano-antennas in scanning near-field optical probe. A novel probe which is added a metallic dipole nano-antenna onto the tip of the ordinary probe is designed and discussed. Based on the FDTD algorithm we investigate numerically the measure results by different aperture probes. The results show that the resolution of the novel probe is 70nm,75nm, 50nm,45nm,50nm,70nm when the probe aperture is 50nm, 100nm, 130nm,150nm,170nm,200nm respectively, and for the ordinary probe the resolution is almost equal to its size. That is to say that the novel probe has greatly advantage of resolution when the aperture is large.we obtain the resolution of 45nm as the aperture is 150nm,which made the probe become "thicker and brighter", eased the contradiction between resolution and sensitivity of the conventional probe, which is also helpful for reducing the difficulties in making the probe. The result also show the sensitivity and contrast have apparent improvement compared to the traditional probe,which contributed a technical approach for improving the SNOM's resolution.