Theoretical And Experimental Study On Subwavelength Circular Polarization Dichroism Devices

Due to the wide applications of circular polarization dichroism?CPD?devices in various optical techniques,ranging from Full Stokes polarized imaging,quantum computation,spin optical communication,optical display to bio-optical imaging and circular dichroism spectroscopy.At present,the relative lag of theoretical design and experimental process technology of high performance and integrated CPD devices is a bottleneck restricting the development of related technologies.In this paper,we focus on the mechanism and characteristics of subwavelength CPD devices,and design and process high CPD,wide operation waveband CPD devices.To satisfy the application requirements of full polarization imaging,we design and experimentally study of all-dielectric pixelated Full Stokes polarized imaging devices.The main contents and innovations of this research are as follows:?1?We propose and experimentally demonstrate a broadband and high efficient circularly polarizing dichroism device using a simple single-cycle and single-helical plasmonic surface array arranged in square lattice.The numerical simulation shows that the CPD of the structure is more than 90%in the mid-IR range?3-5?m?.Then,the CPD of the multi-cycle helical surface structure is simulated theoretically,and the result of CPD is more than 80%in the 4.0-8.5?m range.In order to obtain the easily fabricated 3D helical surface structure,a completely covered helical surface structure with gold film is designed.The numerical simulation results show that the CPD of the structure is more than 70%.The completely covered helical surface array structure is fabricated by 3D laser writing technique.The average of the CPD is 50%?up to 65%?in the 3-5?m waveband in experimentally.Experimental measurement results of the CPD are in excellent agreement with the theoretical simulation,which will lay the foundation for the practical application of the device.?2?We propose and experimentally demonstrate a high efficient circularly polarizing dichroism device using a Z-shaped slot antenna etched into silicon thin film in which are deposited on a silicon oxide substrate.The average CPD of the structure is more than 75%in a wider waveband?1.49-1.61?m?in simulation;The highest CPD can be close to 100%and the extinction ratio I_RCP/I_LCP up to 345(I_RCP,right-handed circularly polarized light transmittance,I_LCP,left-handed circularly polarized light transmittance).We also find that the device exhibits a unique dichroism in that it functions as a transmissive quarter waveplate for one of either left-or right-handed circularly polarized incident lightand a reflective mirror for the opposite polarization.Based on the chemical vapor deposition method,electron beam exposure direct writing process,inductively coupled plasma etching and other processes,an all-dielectric metasurface 2D"Z"chiral structure is fabricated.The experimental results show that the average CPD of the device is above 55%in the1.52-1.62?m range,and the experiment verifies the special optical properties of the device.?3?Based on the advantages of high CPD,easily intergration and compatible with standard semiconductor fabrication techniques in the all-dielectric metasurface"Z"chiral structure,we propose and experimentally demonstrate an all-dielectric pixelated micropolarizer with multi-directional linear polarization and circularly polarized structures,which can be used to Full Stokes polarimetric imaging.In theory,the extinciton ratio?10log?TM/TE??of the all-dielectric linear polarizer is above 20d B and a maximum of75dB in 1.47-1.70?m range.The transmittance of TM light is close to 100%in1.47-1.70?m range.For"Z"shape CPD devices,the CPD is above 75%in the 1.49-1.61?m range.We also design and fabricate an all-dielectric pixelated micropolarizer in which can be used to the Full Stokes polarimetric imaging with commercial silicon-on-insulator?SOI?.In theory,the extinction ratio of linear polarization device is above 20dB and a maximum of 70dB in 1.47-1.54?m range;the CPD of CPD device with the same material is more than 60%in the 1.47-1.54?m range and the CPD is about 90%at 1.6?m wavelength.The experimental shows that the extinction ratio of all-dielectric polarizer is above 20dB in1.47-1.55?m range and close to 20dB at 1.6?m wavelength.The CPD of all-dielectric CPD device is about 55%in 1.48-1.53?m range,and is 70%at 1.6?m wavelength.Therefore,the all-dielectric pixelated micropolarizer can satisfy the requirements of Full Stokes polarimetric imaging in 1.48-1.53?m range,and 1.6?m wavelength.