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Research Of New Optical Devices Based On Metal Structure Metasurface

Posted on:2017-01-30Degree:DoctorType:Dissertation
Country:ChinaCandidate:W WangFull Text:PDF
GTID:1108330503969927Subject:Physics
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In recent years, the optical technology has been widely used in micro-nano fields, and the control of light has received more attention. Generally speaking, the manipulation of light is achieved by regulating the phase of light. Recently the concept of metasurface is put forward, arbitrary phase distributions can be achieved by designing the artificial microstructure in subwavelength scale and the macroscopic order, thus the control of wavefront can be realized. Through the reasonable design of structure parameters, the miniaturization and integration of metasurface optical devices can be achieved. In this dissertation, we mainly focus on how to control the amplitude, phase and polarization states by metasurface, and design the polarization-dependent and polarization-independent optical devices with various functions. The main work and researches of this dissertation are summarized as follows.We propose the polarization-dependent and polarization-independent broadband beam deflectors based on the split ring resonators and L-shaped nanoantennas, respectively, and study their beam deflection performance through theoretical analysis and numerical simulation. The phase shifts from 0 to 2π can be achieved by changing the structure parameters. The beam deflectors both have good beam deflection function, and deflection angles match very well with the generalized Snell’s law. The cross polarized transmitted light of the metasurface based on split ring resonators have opposite deflection direction under the incidence of left and right hand circularly polarized light. The polarization-independence of the L-shaped nanoantennas is proved through theoretical analysis and numerical simulation. We study the polarization-independence of the L-shaped beam deflectors, and find the same bending phenomena of the transmitted light for both linearly and circularly polarized lights.We propose the polarization-dependent and polarization-independent ultrathin broadband vortex phase plates based on split ring resonators and L-shaped nanoantennas, respectively, and find that they both can successfully produce vortex beams. The vortex beams, which are produced by vortex phase plates based on split ring resonators, will have opposite topological charges under the incidence of left and right hand circularly polarized light. The vortex beams, which are produced by vortex phase plates based on L-shaped nanoantennas, will have the same topological charges under the incidence of linearly and circularly polarized lights. That is to say, the vortex phase plate based on L-shaped nanoantennas is polarization-independent. For two kinds of vortex phase plate, we investigate the evolution characteristics of vortex beam, the interactions between light and vortex phase plate, and wide spectrum characteristics, respectively.We propose the polarization-dependent and polarization-independent ultrathin planar metalenses based on split ring resonators and L-shaped nanoantennas, respectively, and find that they both can achieve the desired focusing phenomena. The metalens based on split ring resonators will produce focusing and diverging phenomena under the incidence of left and right hand circularly polarized light, respectively, which indicates that it is a dual-polarity lens, and it is polarization-dependent. The metalens based on L-shaped nanoantennas will produce the same focusing phenomena under the incidence of linearly and circularly polarizedly lights, respectively, which indicates that it is polarization-independent. For two kinds of metalenses, we investigate the focusing characteristics of metalens with different focal lengths and numerical apertures, and wide spectrum characteristics, respectively.We propose transverse multi-focus metalens array and longitudinal multi-focus metalens based on L-shaped slit nanoantennas, respectively, and find that they both can achieve the desired multi-focusing and polarization-independence phenomena. The transverse multi-focus metalens array composed of arrayed sub-lens units, and the co- and cross-polarized transmittence of the sub-lens have different focusing phenomena and focusing principle. Three novel designing methods: partitioned mode, radial alternating mode and angular alternating mode, are firstly proposed to achieve the longitudinal multi-focus metalens. For two kinds of multi-focus metalens, we investigate the influnce of L-shaped slit nanoantennas’ s distribution on focusing characteristics, respectively.We study the polarization-independence of nanoantennas with the symmetrical axis’ s orientation angle of 45° or 135°. Through strict mathematical theory, we find that cross-polarized transmitted lights have the same amplitudes and phase shifts under the incidence of linearly and circularly polarized lights, respectively, whose necessary and sufficient condition is that the nanoantenna symmetrical axis’ s orientation angle is 45° or 135°. Through numerical simulations about V-shaped, C-shaped, U-shaped and elliptical slit nanoantennas, we find that only when symmetrical axis’ s orientation angle is 45° or 135° will nanoantenna be polarization-independent.
Keywords/Search Tags:metasurface, vortex phase plate, metalens, phase modulation, polarization-independence
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