Research On Polarization Control Based On Artificial Metasurfaces

As an important attribute of electromagnetic waves,polarization plays an important role in the study of the regulation of electromagnetic waves.Polarization control technology is a very important research content,and has important applications in the fields of optical communication,polarization imaging,precision measurement,and biosensors.Despite the traditional polarization control methods,the artificial metasurface-based polarization control technology is becoming more and more popular.This technology is simple in preparation,small in size and wide in use,and can flexibly control the phase and amplitude of electromagnetic wave in each band.This paper mainly designs the reflective and transmission polarization control devices based on the artificial metasurface,which the specific research results are summarized as follows:1)Two kinds of reflective polarization control devices working in the infrared band are proposed,both of which are three-layer structure(metal-medium-metal).The first device is a reflective half-wave plate with single L-shaped antenna and the second is a quarter-wave plate with a double L-shaped antennas.In contrast to the conventional wave plate,the proposed QWP is a simple combination of two HWPs.We theoretically analyze the feasibility of the design and simulate the conversion efficiency.The proposed HWP and QWP are highly efficient with bandwidths of 1670-2791 nm and 1592-3867 nm,respectively.the broadband effect of the half-wave plate is determined by the peak,and the quarter-wave plate is caused by the superposition of the three resonance eigen wavelengths.The working mechanism of half-wave plate and quarter-wave plate was analyzed by coupled oscillator model and physical mechanism.The novel design may be beneficial for the implementation of polarization conversion devices.2)Two kinds of transmission multi-functional polarization control devices working in the visible band are proposed.The design concept of this achievement is to combine a transmissive wave plate with a transmissive dual-function wavefront shaping device to obtain a multifunctional polarization control device.The transmissive wave plate and the transmissive dual-function wavefront shaping device are all of the medium structure.And the dual-function device can realize beam deflection and focusing on x-and y-linearly polarized light,respectively.According to the different wave plates,there are two types of multifunctional devices: One is a multifunctional device designed in combination with a half-wave plate.The device can convert incident y-linearly polarized light into x-linearly polarized light and realize beam deflection.In addition,it can convert incident x-linearly polarized light into y-linearly polarized light and realize beam focusing;The other is a multifunctional device designed in combination with a quarter-wave plate.The device can convert the incident right-handed circularly polarized light into x-linearly polarized light and realize beam deflection,and can also convert the incident left-handed circularly polarized light into y-linearly polarized light and realize beam focusing.The numerical results of the two multifunctional devices are similar to those of the dual-function devices,but the efficiency is reduced.According to the electric field intensity distribution of the unit structure,it can be concluded that the two devices can avoid functional interference and efficiency limitation between the unit cells.This all-dielectric multifunctional device provides a good application prospect for the design and development of functional devices in the future.