基于超光栅的3D打印全介质太赫兹超透镜

3D printing all-dielectric terahertz metalens based on metagrating

超透镜是基于超表面和超光栅的器件,可实现对入射光振幅、相位、偏振等的灵活调控,具有轻薄、易集成的特点。但超透镜的制作周期时间长、成本高,寻找一种易加工、低成本、高效的方法制造超透镜是非常有必要的。本文设计了一种高效波前控制电磁波的太赫兹(Terahertz,THz)全介质超光栅,当电磁波垂直入射时,超光栅将电磁波束弯曲至T-1衍射级。通过仿真模拟可知,当P偏振光入射时,可将83.44%的透射能量集中在T-1衍射级,S偏振光入射时可达到82.73%。基于设计的超光栅,当0.14THz电磁波入射时,设计了数值孔径为0.39的超透镜,利用3D打印技术加工工艺制备,并搭建扫描测量系统验证该设计。测量结果表明,超透镜焦距为114.5mm,与仿真设计相一致,同时测得了光斑的大小,最后搭建的THz透射成像系统表征了超透镜的成像能力。这项工作在光学传感、通信和超分辨率成像中具有潜在的应用价值。

Metalens is a device based on metasurfaces and metagrating,which can flexibly regulate the phase,polarization,and amplitude of light.It has the advantages of lightweight and easy-integration.However,the fabrication cycle time of metalens is long and the cost is great,and it is extremely necessary to find an easy-to-process,low-cost and high-efficient method.In this work,an all-dielectric terahertz(THz)metagrating with highly efficiency wavefront control in THz range is proposed.The all-dielectric metagrating bends the electromagnetic waves beam into the T-1diffraction order when the electromagnetic wave is incident normally.In the simulation,more than 83.44%of the transmitted energy is concentrated in the T-1diffraction order for P-polarized light and more than 82.73%for S-polarized light.Then,based on the all-dielectric metagrating,a metalens with numerical aperture of NA=0.39at 0.14 THz is proposed,the metalens has been fabricated by 3Dprinting.The focusing capability of the metalens is characterized by utilizing the scanning measurement system.The focal spot with the focusing distance of 114.5mm is achieved,the measured and anticipated results are satisfactorily congruous with one another,which could validate our design.Meanwhile,the size of the focal spot is obtained.The transmission THz imaging system is performed to characterize the imaging capability of the metalens.This work holds great promise for extensive applications in light sensing,communication,and super-resolution imaging.