Manipulation The Light Based On Artificial Microstructure Metasurfaces And Its Applications

One of the most fundermental issues in optics and nanophotonics can be attributed to exploring the underlying physics of light-matter interaction and developping novel devices to effectively manipulate the light.As a new“artificial”material platform,metamaterials can achieve customized control of electromagnetic waves through artificially engineering the geometric degrees of freedom of the microstructures.Optical metasurfaces,two-dimensional(2D)metamaterials,are artificial microstructure arrays composed of subwavelength metaatoms.Through effective design of the electromagnetic properties and spatial arrangement of the metaatoms,the metasurface provides an efficient,compact,and flexible platform to manipulate the light at subwavelength spatial resolution.It is predicted to have the potential to produce disruptive applications because of the abundant and tunable degrees of freedom and physical mechanism with multi-parameter manipulation.For infrared optics with many major applications of photoelectric technology,it is of great significance to develop miniaturized,efficient,and multi-functional integrated photonic devices based on the powerful capabilities of the metasurface.This thesis mainly focuses on silicon-based infrared metadevices with effectively engineering the orbital angular momentum,polarization,and broadband phase dispersion of the light.The main contents are as follows:1.We have studied the generation of focusing optical vortices(FOVs)and the detection of orbital angular momentum(OAM)based on the transmission-type high-contrast metasurface(Si/Si O₂)with high efficiency.Through analysing the evolution forms of the focusing optical vortex wavefronts and optimizing the electromagnetic response parameters(transmission and phase)of the metaatoms,the wavefronts have been reconstructed via the metasurfaces.Subsquenctly,the near-infrared(1550nm)OAM beams can be generated with focusing efficiencies from 70%to 85%.Besides,the interaction between optical vortices and the metasurface has been studied.From the perspective of annihilation of OAM,we have explored the generation of multichannel FOVs and and the detection of OAMs based on the metasurface via the principle of interference holography and off-axis configuration.2.We have proposed the theoretical model of multi-parameter manipulation of the polarization and phase dispersion.The design strategy of multifunctional broadband achromatic metadevices in MWIR has been also established.We have also verified the methodology experimentally.A double-sided polished silicon wafer is used to fabricate two broadband(3.5-5?m)polarization-controlled achromatic focusing metadevices(BAFOV-metasurface and BAFS)with high numerical apertures(D=200?m,NA=0.45).First,we have studied the performance of BAFOV-metasurfce for wavefront shaping,achromatic focusing and polarization control of broadband incidence.The broadband incidences with different polarization are achromatically focused into FOVs with different OAMs.In addition,by introducing off-axis phase gradient,BAFS has been constructed.Within the continuous bandwidth,the BAFS can selectively and achromatically focus photons with different polarization states to different positions prescribed on the focal plane.The focal spots are nearly diffraction-limited.3.Geometric phase-based broadband achromatic metalenses are dependent on the polarization state of the incidence and the function is single.Here,based on the all-silicon metasurfaces,polarization-insensitive broadband achromatic metalenses with high numerical aperture(NA=0.45)have been realized in the mid-wave infrared ranged from 3.5 to 5?m.Experimentally,we have verified the broadband achromatic and diffraction-limited focusing and broadband imaging performance of the fabricated metalens.The polarization-controlled varifocal achromatic metalens and the broadband achromatic focusing optical vortex have been successfully achieved,which further develop the photon manipulation dimension of the broadband achromatic metalens.4.Based on the metasurface with Si₃N₄/Si double-layer heterogeneous configuration,we have proposed a new design strategy for high-efficiency dispersion-controlled metasurfaces in mid-wavelength infrared(MWIR).The physical mechanism of the free spectrum parameters is clarified for the design of broadband and multi-wavelength achromatic metalenses.By depositing a sub-wavelength-thick Si₃N₄ layer on the all-silicon metasurface,we have further expanded the tunable degrees of freedom.The broadband achromatic metalenses with high efficiency have been explored in MWIR from 3?m to 5?m(50%of the central wavelength bandwidth).The designed achromatic metalenses(NA=0.24,NA=0.45)have achieved broadband focusing efficiencies of about 70%and 62%,respectively.In addition,through flexibly engineering the phase profiles at multiple discrete wavelengths,multifunctional metadevices with wavelength regulation are designed.Based on the multifunctional metadevices,we have realized achromatic focusing beam splitting for multiple discrete wavelengths and the generation of wavelength-controlled focusing optical vortices(?₁=3.5?m L₁=-1,?₂=4.25?m L₂=0,?₃=3.5?m L₃=1),respectively.