Terahertz Beam Steering Based On All-dielectric Sub-wavelength Asymmetric Antenna Array

Terahertz wave,lying in particular position between the microwave and infrared spectra in the electromagnetic spectrum,has many unique properties such as fingerprints,living safety,and transmission of non-polar materials,finding it promising applications in non-destructive testing,homeland security and medical diagnosis.However,traditional beam steering devices based on the optical path accumulation such as lenses,prisms,and reflectors are bulky and heavy.In recent years,metasurfaces based on sub-wavelength structure arrays with scattering pattern have shown great advantages in ultra-flexible and ultra-slim beam steering.In this paper,we proposed a sub-wavelength asymmetric array antenna used for metagrating to efficiently manipulate terahertz waves.The main researches have been summarized as follows:1.Metagrating diffraction based all-silicon subwavelength asymmetric antenna array used for high efficiency and large angle bending terahertz wave is designed.It can be achieved by breaking the symmetry of the gratings in array that channeling light energy into desired diffraction order and suppress the one in other orders.Our all-silicon micro-antenna is designed by solid and hollow cylindrical unit structure at the working frequency of 0.3THz.When P-or S-polarized plane wave incident,light energy can be guided into the first diffraction order(T_-1)at the angle of 70.2°with efficiency of 73.1%and 37.8%respectively.Meanwhile,we discussed several effects on transmission efficiency of changing in different parameters,material of base and comparing with existing structures.The choice of all-silicon solution is not only for its high refractive index and low loss in terahertz range,but for reducing fabrication complexity and cost.2.Based on metagrating,two kinds of high-efficiency bending terahertz wave micro-antenna arrays at working frequency of 0.1THz with 3D printed material ABS are designed.For the micro-antenna array with a deflection angle of 66.6°,the measured transmission efficiencies are 74.1%and 54.2%under S-or P-polarized incident wave,respectively.For 37°micro-antenna array,the measured transmission efficiency is 67.1%and 56.4%under S-or P-polarized incident wave,respectively.3.Two kinds of diffractive metagrating based flat lenses with 3D printed materials are designed by asymmetric micro-antenna,of which the frequency are both 0.1THz with diameter of 100mm.The two flat lenses have numerical aperture of 0.91 and 0.6with simulated focal lengths are 23.3mm and 65.6mm.Measured results of focal lengths are 24mm and 66mm with the focusing efficiency of 32.1%and 50.3%.