The Researches On The Near-infrared Optical Devices Based On The Dielectric Metasurfaces

In recent years,the design of the planar optical devices has become important research and hotspot for the development of photonic integration and optical chips.Traditional optical devices are made of natural materials,which has great bulk and their control methods are relatively simple.Besides,it is difficult to achieve on-chip integration,polarization control of electromagnetic waves,miniaturization,and so on.Due to its sub-wavelength dimension,integration,and ability to arbitrarily control the wavefront of electromagnetic waves,the metasurfaces have become the great choice for the design of optical devices.However,as a kind of materials of the metasurface,the extremely high metal loss of the metal makes the designed optical devices have extremely low efficiency.This article focuses on the related design and application of optical devices based on dielectric metasurfaces by the finite-difference time-domain method.The concrete researches are as follows:(1)An ultra-thin dielectric metasurface based on the silicon nano-brick arrays with extremely high transmittance was proposed.By adjusting the length and width of the silicon nano-brick,the incident x-linear polarized light and the y-linear polarized light can achieve 0 to 2? phase control,respectively.In addition,the two phase controls are independent of each other,and both have the transmission of the co-polarized light over 90%.Based on the dielectric metasurface,we designed an polarization beam splitter operating in the communication band(1500nm),which can deflect two orthogonal linearly polarized light to different angles.We also designed a polarization-independent beam deflector based on the designed dielectric metasurface.By changing the lattice constant of the metasurface and the number of antennas in a supercell,any deflecting angle can be achieved.In addition,in order to obtain the concrete XLP and YLP compositions in the transmitted fields in real experiments,we designed an ultra-thin metalens to focus the two orthogonal polarization compositions in different positions.(2)A high-efficiency polarization beam splitters and optical vortex generators based on high-order dielectric metasurfaces have been designed.Most of the demonstrated optical devices in the previous works use the ±1st order diffraction modes to manipulate the wavefront of light.By modulating the discrete phase distributions in a supercell,we can design the optical devices operating in high-order diffraction mode with high transmission.Based on the dielectric metasurface,we designed two polarization beam splitters with abrupt phase discontinuities and operating in third and fifth order diffraction modes.In addition,we also designed two vortex beam generators with topological cores 2 and 3 operating in high-order diffraction modes.This design method can be extended to other optical transmission devices with high efficiency.(3)Dual-functional devices that combine the waveplate with other optical devices based on dielectric metasurface have been proposed.Based on the theory that our designed dielectric metasurface can simultaneously control the polarization and phase wavefronts of incident light at the wavelength of 1500 nm,we achieved an invertible dual-functional device that combines the quarter-waveplate with the beam deflector,whose transmitted efficiency is over 70%from 1360 nm to 1640 nm.Besides,we designed other three dual-functional devices,including half-waveplate/deflector,quarter-waveplate/focusing-lens,and half-waveplate/focusing-lens,which verify the feasibility and practicality of our designed dual-functional devices and are beneficial to the miniaturization and integration of optical devices.