Manipulation Of Optical Fields Based On Subwavelength Metallic Structures

Optics and condensed matter physics are two major branch disciplines of physics,investigating the optical properties of materials is the intersection of these twodisciplines. The propagation of light in the material is described by the classicalMaxwell equations. Starting from the effective medium theory, the material equationintroduces two important parameters ε and μ in order to describe interaction betweenmaterials and light. In principle, as long as the change of ε and μ, we can control lightpropagation. Most materials can have light response, considering the limitations ofconventional materials, to achieve desired optical response is always the dream. Inrecent years, the microstructure materials composed by a special artificial metalnano-micro structure unit, achieves some very interesting phenomena, which aredifficult to achieve in conventional materials, such as negative refraction, super-lens,invisible cloaking, etc.It had a profound impact in the fields of science in the early21st century. In view of development and research of subwavlength metallicstructures, the manipulation of optical fields tend to focus on the macro-manipulationof the amplitude and phase (dispersion), and little attention to the manipulation ofpolarization, presenting the vector nature of light. Extended the manipulation ofoptical fields to subwavelength scale, the investigation to the interaction betweenlight and metal micro-structural unit is very important, especially light fieldpolarization control in subwavelength scale. The main content of this thesis is tostudy the interaction between several types of micro-structural units and the light inorder to achieve the manipulation of optical fields on amplitude, phase andpolarization.On the basis of previous works, I have done the following specific works:(1) interference cancellation phenomenon not only exists in the quantum system, aregenerally present in the classical system. Overcoming the critical conditions ofelectromagnetically induced transparency (EIT) phenomenon, to find a similarphenomenon in the classical system has been the dream. Interference cancellation mode realized by subwavelength metallic micro-structural materials, produces theformation of the transparent window, and has a very strong dispersion in the vicinityof the transparent window in order to achieve the phase control of the light field, sothe group velocity of light slows down. In analogy of the EIT mechanism in atomicsystem mechanism, and the Fano resonance, and the Fano resonance, we design thespecial subwavelength metallic structure based on the Interference cancellation mode,and verify the analogy in order to provide reference to other disciplines. In thischapter, we discuss the realization of Fano resonance and Fano-Feshbach resonancethrough the use of subwavelength metallic structure.(2) Considering to the unit of subwavelength metallic structure, people tend to focuson very simple and high symmetry unit electromagnetic response, while ignoringinfluence of the unit symmetry on the electromagnetic response. We achieve theasymmetric transmission of electromagnetic waves based on the unit symmetry. Onthe basis of a detailed discussion of the origin of asymmetric transmission forcircularly polarized electromagnetic wave, we analyze the possibility to achieve theasymmetric transmission for linearly polarized electromagnetic waves; and design thecorresponding metallic microstructure, realize asymmetric transmission only forlinearly polarized electromagnetic waves, while symmetrical transmission forcircularly polarized electromagnetic waves.(3) The angular momentum of the light field is generally divided into two categories:the spin angular momentum (SAM) and the orbital angular momentum (OAM). SAMis usually related to the circular polarization of light. OAM is usually related to thewavefront perpendicular to the light propagation axis. When the incident light iscircularly polarized, carry SAM, a longitudinal field component near the metal holespresents the spin dependent vortex, we reveal the microscopic physical mechanism ofthe longitudinal field component of the vortex, when the incident light carries SAM,and find that the longitudinal component of the electric and magnetic fields bothpresent spin dependent vortex. Further analysis show that the transverse componentof the energy flow also exhibits spin dependent vortex, which has potentialapplication in the manipulation of nano particles. At the same time, we also discussthe role of the surface plasmon polariton on the generation of near-field vortex. (4) We often discuss the optical angular momentum within the range of the beam,which means that the scale of the beam is much greater than the wavelength, i.e. theparaxial approximation, in this case the spin part and the orbital part of the opticalangular momentum can be separately discussed. When we study the scale in thewavelength range or subwavelength scale, the paraxial approximation will not be ableto apply to the optical angular momentum, which is not so easy to distinguish.Subwavelength metallic micro-structure as the basic unit can be achieved effectiveinteraction with the light field in the subwavelength scales. Based on the enhancedtransmission in subwavelength metallic structure unit with strong polarizationdependent characteristics, we construct the inhomogeneous anisotropic metamaterialsat the enhanced transmission peak, achieve the manipulation of optical fields in thesubwavelength scale, and investigate the conversion from spin to orbital angularmomentum in the subwavelength scale. The detailed theoretical and numericalanalysis of the physical processes can be verified. Starting from the basic fact,through the use of simple structure unit, we realize spatial splitting of optical spin,which can be viewed as the photonic version of a Stern-Gerlach(SG) experiment inthe absence of magnetic fields, and realize the optical spin dependent angular shift inmetallic structured metamaterials.