The Optical Device Design And Research Based On Surface Plasmon Polaritons

Surface plasmon polaritons (SPPs) are electromagnetic field from the coupling between the light and the free electrons on the metal surface. Their fields are strongly confined on the metal surface, and decay exponentially when departing away from the metal surface. Moreover, the extraordinary optical transmission effect in subwavelength metallic structures can effectively increase the transmittance of light. This properties of SPPs are very conducive to the realization of compact nanofocusing devices, which have great application potential in nanoscale beam shaping, integrated optics, data storage, lithography, and super-resolution imaging. Hence, various metallic structures based on SPPs were designed to realize nanofocusing and increase the focusing intensity.In this thesis for the master degree, I first optimize the hybrid waveguide structure, which proposed by Van Duon Ta in2011. Through utilizing air pillars additionally added to original structure and a photorefractive polymer film(PPF) added on the sliver substrate, enlarging the propagation length from628u m to1514μm and decreasing the size of spot from2.17e-6μm to1.2e-6μm.Then based on the research of previous nanofocusing devices, we provide a new route to designing devices. Compared with previous nanofocusing structures containing plenty of substructures arranged laterally, the proposed structure has a much smaller lateral dimension because of the vertical arrangement of themicroslits, whose lateral dimension is only2μm. Highly efficient plasmonic nanofocusing is numerically predicted in a single step-like microslit, which is placed on a high-index dielectric layer. Because of the high throughput of the impinging light on the wide microslit, highly efficient nanofocusing is achieved in the proposed structure based on the multimode interferences in the microslits, the constructive interference between the transmitted light and the scattered surface plasmon polaritons, and the Fabry-Perot resonator effect in the high-index dielectric layer. As a consequence, a high focusing intensity of about I=5.1and a spot size of only about FWHM=300nm (<λ/2)were achieved.Next through change the parameter of the thickness of gold film and the width of slit in the single step-like microslit, successful etched this structure in a thickness of500nm gold film using focused ion beam in experiment.Finally, this study designed a single step-like nanoslit construction, which can achieve focusing on the focal length of600nm. When the incident wavelength of830nm, through numerical simulation obtain the two-dimensional spot size of FWHM=423nm, and the three-dimensional spot size of FWHMx=426nm, FWHMy=690nm, and observed the foucsing phenomenon in experiments successfully.In all, we theoretical proposed and experimental verification a new design method of nanofocusing device, this method has the flexibility to be focused on the different wavelengths by changing the structural parameter. And the proposed sub-structure with a vertical arrangement, with a smaller horizontal dimension, conducive to the integration of the device.