High Aspect Ratio Au Nanohole Array Fabrication And The Compensation Of Plasmon Damping By Quantum Dots

Surface plasmons havemany optical merits including light concentration beyond the diffraction limit,high sensitivity to environmental refraction change,and ultrafast response,all of which can be manipulated via structure design.That makes it useful in a variety of areas,such as solar cells,sensors,medication and security.The main factor that limits their application is the high optical absorption inherent to metals.Therefore,the quest for minimizing dissipative damping has been a crucial driving force for plasmonics.The endeavour of improving plasmonic performance,most notably by reducing optical loss,has been accomplished by the pursuit of materials that outperform noble metals in specific optical functionalities.Different options,such as aluminum,metallic alloys and heavily doped semiconductors,have all been investigated,which advances our understanding and broadens the catalogue of available plasmonic platforms.And the combination of gain media and metamaterial make it possible to create loss overcompensation and surface plasmon amplification by stimulated emission radiation.The gain medium is excited and population inverted by an external source,which produces electron–hole pairs in it.These pairs relax,to form the excitons.The excitons recombine,emitting SPs in the nanoshell.The plasmonic oscillations of the nanoshell stimulate this emission,supplying the feedback for the spaser action.The plasmons in the spaser mode create the high local fields that could be used to enhance the sensitivity of sensor.The geometry of nanostructures determines the distribution of local field that makes it possible to control the electronic field by tuning the surface topography of nanomaterial.On the other hand,the faults in the nanostructure also affect the optical characteristic heavily under the character of flexibility in design.Nanosphere lithography is an economical technique for generating nanohole arrays.While the faults embed in the colloidal spheres monolayer can't be purged thoroughly and the method is not so efficienct on self-assembly.On the other hand,this technique is not so impactful to get rid of colloidal spheres template.A modified set is built to realize the high throughput fabrication of the large-area 2D single-sized and binary PS SAMs and the nanopillar arrays of poly(methyl methacrylate)(PMMA)have been used to make the nanospheres lithography more controllable in nanostructure design.Finally,the quantum dots were used as gain media to study the loss compensation and spaser action.The main contents and conclusions are as follows:(1)Macroscopic Domain of Polystyrene Nanospheres Self-Assembled at the Air/Water Interface.A facile method is developed to realize the high throughput fabrication of the large-area 2D single-sized and binary PS SAMs with various diameters ranging from 100 to 1300 nm at the air/water interface with the help of Marangoni effect.The area of monolayer is about 100 cm~2 which is constrained by the size of the water surface.And the size of a single domain could be expanded to macroscale(0.5mm~2)by adding ammonia to water subphase and decreasing the subphase temperature.they are synergistic effects of capillary,van der Waals,electrostatic force and thermodynamic force that result in the formation of 2D colloidal crystal.This technique is simple and effective to be applied into the industrial fabrication of high throughput 2D colloidal crystals.(2)The fabrication of nanohole arrays with high aspect ratio and its optical character.ThePMMA Nanopillars array created by transferring the pattern consist of PS and used as template to prepare high aspect ratio nanohole arrays.Their structure character determines the distribution of hot spots in the nanohole arrays.The FDTD-solutions is used to monitor the position of electronic field.It was found that the location and intensity of field of local surface plasmon and surface plasmon are determined by the thickness of nanoholes.If the thickness of nanohole arrays is about 30 nm,the intensity of localized field of LSPR is stronger than the field intensity of SPR,but when the thickness increases to 70 nm,the situation is contrary.The sensitivity is in proportion to the intensity of field,so effective methods should be created to enhance the field,such as multilayer structure of metal and diameter.(3)The fabrication of quantum-dots-Au-nanohole-arrays and its optical character.The main factor limiting their use is the high optical absorption inherent to metals.Therefore,the quest for minimizing dissipative damping has been a crucial driving force for plasmonics.The gain media is used to make loss compensation and spaser.Some structure is designed to expose the hot spot based on the structure and index effects.