Theoretical Studies Of Light Manipulation And Spectroscopies Based On Metasurface

Optical metasurfaces are composed of ultra-thin two-dimensional subwavelength antenna arrays ultrathin two-dimensional structures.It not only has the ability to efficiently control the properties of light wave front and polarization state,but also has the function of efficiently generation of vector beam and nonlinear signal.These special types of nanostructures have attracted great interest of researchers in the past two decades.The metasurface can achieve spatially changing optical response at sub-wavelength scale(such as scattering phase,amplitude and polarization state),modulate optical wavefront into arbitrary waveforms and it provides a simple platform for the realization of functional integration.The functional application of metasurface has been extended from linear optical process to nonlinear optical process.Nonlinear metasurface has been successfully applied to nonlinear response enhancement,nonlinear process wavefront and polarization state control,which provides a new platform for ultrafast light manipulation,spectral detection and other related technologies.As a twodimensional branch of metamaterials,metasurface has developed into an independent research field.Because of its two-dimensional structure,higher work efficiency and stronger degree of optical control,metasurface is promising to become a new generation of high-performance integrated micro optical devices.The main contents of this paper describe theoretical studies which are focused on the wavefront control and spectroscopic methods based on metasurface in the following three aspects:(1)Using the linear scattering theory,we establish a linear mesoscopic electrodynamics model based on the classical Maxwell equations to study the polarization conversion properties of each scattering order of Pancharatnam Berry(PB)metasurface.Then,the equal-amplitude beam splitting of the same polarization state and cross polarization state is realized.By analyzing the phase factor of scattered light,the constructive or destructive interference between the constant phase and the spatially uniformly varying PB phase on the metasurface leads to the stable chirality dependent transmission characteristics of PB metasurface.Furthermore,the angular dispersion properties of the metasurface are analyzed theoretically.In the experiment,PB metasurface is fabricated based on Ga N nano antenna arrays.Combined with the analysis of the theoretical model,the metasurface has the function of 50 / 50 beam splitting by using the ?/4propagation phase delay in the direction of x,y of a single antenna.Thus,using this metasurface as a beam splitter,a Mach-Zehnder interferometer is built to measure the linear change of the anomalous transmitted light phase along the x axis caused by the PB phase gradient.(2)Based on the linear mesoscopic electrodynamics model and combined with the robust phase and polarization modulation ability of PB phase,we propose a new strategy to realize multi-channel multiplexing of PB metasurface.The transmission of different polarization states in seven channels can be realized by flexibly setting two different staggered PB phase distributions in two rows of identical birefringent nanoantenna arrays.The analysis of the control parameters of each polarization state shows that their polarization states can be controlled by different independent PB phases.This scheme can avoid the dependence on the propagation phase in the modulation,thus enhancing a more stable degree of freedom improving the overall design.(3)Using the nonlinear polarization response and linear mesoscopic electrodynamics model,we establish a nonlinear theoretical model to study the scattering mechanism of nonlinear signal when passing through the PB metasurface.By analyzing the phase factor of scattered light,the constructive or destructive interference between the constant phase and the spatially uniformly varying nonlinear PB phase on the metasurface leads to the stable chirality dependent transmission characteristics of PB metasurface.In this part,we present the simultaneous generation of circularly,elliptically,and linearly polarized states by the simplest PB metasurface with one-dimensional phase gradient unit cells.Furthermore,we propose that the reconstruction of a multidimensional nonlinear polarization response of a nanomaterial can be achieved in a single heterodyne measurement by active manipulation of the polarization states of incident light.Using multidimensional spectroscopy,we demonstrate the possibility to track both stationary and transient delocalized charge distributions via detecting plasmonic populations and coherences.