Study On Spatial Filtering Properties And Spin-dependent Splitting Phenomenon Of Man-made Microstructures

The spatial filter has been widely used in the fields of image enhancement,information processing and laser science.In recent years,the metamaterials has been extensively studied,which is a kind of artificial structure and composite material showing extraordinary physical properties.Considering the disadvantages of traditional spatial filters,such as a relatively large size,impossibility of near-field filtering,we study the spatial filtering characteristics of metamaterials and explore the designs of the plug and play(non-focusing type)spatial filter by using the transfer matrix method and other numerical algorithms.Furthermore,the regulation of the spin splitting of Gauss beam in the man-made micro structure is studied.Some results can be obtained as follows.Firstly,a photonic crystal structure which extends the absolute gap is proposed,and the influences of various structural parameters on the bandgap are explored.It is shown that the absolute bandgaps of the photonic crystals are increased by tuning the two kinds of magnetic material's parameters properly and increasing the difference between the two wave impedances.By adjusting the physical thickness of two kinds of magnetic materials,the center of the absolute bandgaps can also be adjusted.The above two kinds of one-dimensional magnetic photonic crystals compose the heterostructure and the ratio of the first bandgap to the center of the bandgap can reach more than 1.41.Secondly,the metamaterials and quasi periodic structures are used to design low-pass spatial filters with small angle-domain bandwidth separately and the influences of structural parameters on the angular domain bandwidth are explored.It is shown that the low-pass spatial filters with small angle-domain bandwidth designed by using metamaterials are polarization independent,and the angular bandwidth is not affected by polarization.The angular bandwidth of the low-pass filter with small angle designed by using the quasi periodic structure can realize rough adjustment and precise adjustment,and the filter is more suitable than the former in high-power laser systems.Thirdly,a novel approach is presented for waveguide mode selection by using thin-film spatial filters embedded in multimode waveguides.The waveguide modesare allowed to pass through the spatial filters if and when their mode angles fall within the angle-domain bandwidth of the filters.Consequently,the waveguide modes are selectable by adjusting angle-domain bandwidth of the spatial filters.This approach is relatively simple,cost-effective and features good suppression effects of high-order modes.Finally,the manipulation of spin splitting in spin Hall effect of light based on the dynamic and geometric phases is systematically investigated from the theoretical and experimental standpoint.The geometric phase controls the size and direction of the spin splitting of the beam,while the dynamic phase controls the overall translation of the beam.An experiment system is established based on spatial light modulators and meta-surfaces,and the possibility of realizing manipulation of spin splitting in spin Hall effect based on dynamic and geometric phases is experimentally confirmed.