Investigation Of The Dispersion In Metasurface With Multiple Wavelengths Or Broadband Illumination

Metasurface is a kind of two dimensional(2D)novel material consists of sub-wavelength structures.On one hand,it is ultra-light and ultra-thin,thus,it has potential to replace traditional optical materials to realize minimized and light weight optical devices.On the other hand,due to the capacity of electromagnetic amplitude and phase control on sub-wavelength scale,artificial structures can be designed to achieve special electromagnetic responses to frequency and polarization.Therefore,metasurface can realize the functions which are unachievable in traditional optics and has great potential in the integration of optical devices.Metasurface has been designed to realize functions including beam shaping and beam control,special beam generation and hologram since it was proposed.It has great potential in plenty of areas,including imaging,detection,spectropy and fabrication.However,the factors,such as difficulty in large area fabrication,electromagnetic loss and chromatism limits the metasurface in real application.In this thesis,we investigate one of the key factors of such limitation on the dispersion and chromatism.Most recently,some methods of dispersion and chromatism control and compensation are proposed.However,due to the discretization of wavelengths and the paramter requirements for resonance,it is still hard to solve the issues of metasurface in multiple wavlengths or broadband applications such as imaging and communication.Focused on the dispersion and chromatism of metasurface,the dispersion and chromatism control of metasurface is investigated in this thesis.Main achievements of this thesis are listed below:1.A metasurface is designed to realize polarization independent band-stop filtering working at terahertz band on flexible substrate.It can be fast and efficiently fabricated by micro-lens array laser fabrication system.The bandwidth of 0.291 THz for a single layer metasurface and 0.461 THz for the stack of multiple metasurfaces together are experimentally achieved.Via numerical simulation and theoretical analysis,the amplitude dispersion of antenna and coupling between antennas are investigated as the foundation of the research on related devices with varied bandwith.2.A method is proposed to achieve achromatic flat optical components via compensation between structure and material dispersion.An achromatic model is built in the unit cell of metal-insulator-metal(MIM)waveguide.The differences of achromatism in metasurface and traditional optics are discussed.Ultra-broadband continuous achromatic metasurface beam deflector and lens are achieved at the wavelength from 1 ?m to 2 ?m.3.Using the dispersionless phase shift of dipole antenna and multiple wavelengths off-axis illumination technique,a color hologram based on metasurface is realized.By spatial frequency control,high quality two-dimensional and three-dimentional holographic restructrured color image is demonstrated in experiment.By such kind of method spatial frequency space of metasurface can be fully used,which provides unachievable advantage compared with traditional optics.4.A theoretical model is built to realize orbital angular momentum(OAM),wavelength and polarization simultaneously by a single metasurface via utilizing the dispersion and polarization response of metasurface.This function is corresponding to the three main multiplexing techniques in optical communication including space-division multiplexing(SDM),wavelength-division multiplexing(WDM)and polarization-division multiplexing(PDM).By numerical simulation and some initial experimental resutls,the functions of multiplexing and demultiplexing are demonstrated.