Study On Surface Plasmon Absorption Characteristics Of Metal Micro-nano Structures

The energy problem has always been the focus of our attention.Solar energy,as an inexhaustible energy,plays a vital role in solving the energy problem.People have been using solar energy in various aspects.Light is an electromagnetic wave.When light shines on a metal,the incident electromagnetic field will excite free electrons on the Surface of the metal to oscillate together.This is called Surface plasmons（SPs）,which can be used by focusing light on metals.Up to now,a large number of materials have been made into various structures,commonly used metals and their derivatives mainly include:gold,silver,titanium,aluminum and so on.They are made into metal triangles,metal grating,nanospheres,U-shaped slots and other shapes,and are applied in various fields.Metal gold is a very common light absorption material.It is stable and has very good absorption effect in visible light range.Using the characteristics of gold to make a variety of structures,you can get different effects.This paper mainly studies the optical properties of metal nanostructures and explores the application of gold in different structures.We mainly use simulation software to adjust the geometric parameters of the structure,and indepth use of electromagnetic field,impedance theory and so on to explain the light absorption performance,and finally put into concrete applications.The thesis mainly includes the following aspects:1.The influence of various parameters of golden Triangle MIM structure on absorption spectrum is studied in detail,and the electric field cross section diagram of absorption peak location is analyzed,and the isoionization resonance mode of each absorption peak is obtained.Finally,the best absorption spectrum was found.However,the absorption did not reach a very ideal state,so we improved the structure and replaced the golden triangle with gold and silver triangle.By adjusting the structural parameters,we explored the influence of various structural parameters on the absorption and found a nearly perfect absorption spectrum line within the visible light range.The absorption spectra at different incidence and polarization angles are calculated.The results show that the model with high symmetry is insensitive to incident Angle and polarization Angle,and the reason of high absorption is explained by impedance theory.Finally,the solar photothermal conversion efficiency is calculated,which confirms that our designed structure has a very high application of photothermal conversion.2.The effect of the structure parameters of the U-groove array on the absorption spectrum was studied in detail.At the same time,the influence of the length of the twodimensional structure was calculated to confirm the possibility in the experiment.Finally,a spectral line with a very narrow half-peak width and a very high absorption peak was found and compared with the U-shaped groove directly placed on the substrate of the medium.By calculating the electromagnetic field of the absorption peak,it can be seen that the high absorption is mainly caused by magnetic resonance,thus confirming that this phenomenon is very similar to Rabi splitting in atomic physics.Finally,we changed the refractive index of the air.With the change of refractive index,the position of absorption peak is obviously shifted.It can be seen that the position of absorption peak has a linear relationship with the change of refractive index of air.The refractive index sensitivity of ultra-narrow bandwidth mixing mode of gold VSRRs structure on the gold substrate is quite high.Its quality factor is 18 times higher than that of the U shape placed directly on the medium,and it is also the most improved structural material discovered so far.The structure is simple and convenient to manufacture,and can be mass-produced.It has a great prospect in the application of air sensors.