Surface Plasmon Based Nanostructures Manipulating Light Transmission And Absorption

Surface plasmon(SP) is a kind of surface wave propagating along the metal/dielectric interface produced due to the interaction between electrons and the incident photons. Since it can manipulate light in the subwavelength scale, SPs have been applied in traditional optical devices aiming for the miniaturization as well as improving the performances. This thesis includes our endeavors on manipulating the transmission and absorption of light by SP based nanostructures.In the aspect of light transmission, we have designed a novel thin film beam collimator. The reported thin film beam collimators are generally the bull’s eye structure comprising of a nano hole in the metal film and a shallow grating etched around the hole output surface, which is very difficult to fabricate. Here, in chapter 2, instead of using the traditional bull’s eye structure, we have designed a beam collimator based on the combination of a metal/dielectric multilayer film and a metal grating, in order to avoid the fabrication of nanometer sized hole, thereby lowering the fabrication difficulty as well as reducing the cost. The optimized beam collimator is able to reduce the divergence angle of the Gaussian wave from 6.51o to 3.36o. This chapter also present the dependence of the beam collimation performance on the structural parameters in detail.In the aspect of light absorption, we apply SPs in organic solar cells(OSCs). Although there are a large number of reports having pointed out that SPs can improve the light absorption in the active layer of OSCs, however, very little work has pointed out whether the selected reference is the optimal planar cell or not, which may result in the ability of increasing light absorption in the active layer produced by SP based elements overrated. For clarifying this issue, in chapter 3, we select a typical case and carry out detailed theoretical investigation on the SP enhanced absorption in OSCs. In detail, an inverted OSCs based PTB7: PCBM is taken as the investigated system. In the active layer of different thicknesses, we have introduced a periodic array of metal strips. Through the global optimization of all the structural parameters of the metal strips, we can obtain the best SP based OSCs. Then, we summarize the rule of absorption enhancement in the active layer produced by the metal strips by comparing the best SP based OSCs with the planar OSCs when the thickness of the active layer is tuned.Finally, the summary and outlook are presented.