Research On Light Field Control Characteristics Of Composite Plasmon Grating Structures

With the advancement of modern micro-nano processing technology and the deepening of basic theoretical research,the research on the properties and applications of surface plasmons has become an important branch of nano-optics.Surface plasmons have unique optical properties.Surface plasmons have shown significant advantages in light-field control at the nanoscale,which provides wide application in micro-nano photonic devices,near-field optics,surface-enhanced Raman spectroscopy,biosensors,and many other fields.The plasmonic gratings are widely used nanostructures,due to their ease of large-scale preparation and low cost,among which the composite grating structures have shown better performance in light-field control.This thesis mainly included the following research results:(1)A spatially pinned surface plasmon is constructed by connecting a gold nanoshell grating with a planar gold nanofilm,forming a periodical array of gold nanoloops.Dramatic electric field modulation and high charge carrier density on the contact sites enable balanced plasmonic electron distribution over the spatially pinned nanostructures.Compared with its counterpart,spacer-supported double-layer surface plasmon polaritons,the pinned structure not only changed the electronic oscillation channels but also short-circuited the propagating SPPs at the top and bottom interfaces.Ultrafast spectroscopic dynamics identified a much-extended relaxation lifetime of the pinned plasmon and revealed a holding time as long as 1.3 ps for the double-layer SPPs,which was sustained by microcavities based on distributed optical feedback.These results introduced a new type of surface plasmon and a new design of time retarders for optical logic circuits.(2)A chiral metasurface structure with selective transmission for left-hand and right-hand circular polarization light is designed by the finite element method.The structure is composed of a double-layer Ag/photoresist grating.The circular dichroism can be adjusted by changing the cross angle,period,and height of the two gratings.By optimizing the structural parameters,the circular dichroism as high as 0.7 can be achieved.