Investigations Of The Terahertz Function Devices Based On The Dielectric Metasurfaces

Terahertz(THz)technology,due to its unique nature,has great application prospects in real life,however,because of the lagging development of terahertz sources and detectors,the terahertz technology is limited in practical applications.Meanwhile,the development of terahertz technology is restricted by the complex design of terahertz functional devices.Nevertheless,the designed metasurface structure has received great attentions in recent years due to its stronger ability in manipulating the amplitude,phase and polarization state of incident light.This paper explores specific THz functional devices through designing metasurface,including:(1)We designed several THz functional devices based on silicon micro-brick metasurface.Here,we propose a silicon micro-brick structure to manipulate the terahertz wave by controlling the waveguide resonance generated in the structure,in which by varying the geometric sizes of the Si micro-bricks,the transmitting phase of the terahertz wave can almost span over the entire 2π range for both of the x-polarization and y-polarization simultaneously,while keeping the similarly high-transmission amplitudes(over 90%).Based on this principle,we have designed three types of terahertz functional devices,such as the polarization-dependent beam splitter,polarization-independent beam deflector and dual-focus lens.This designs are easy to developing high-efficiency THz functional devices.(2)We proposed several dual-function metasurface devices with combining wave plates and optical devices.Based on the advantages of the above structure,we design two dual-function devices with combining wave plate and deflection,similarly we also design two dual-function devices with combining wave plate and focus.We successfully designed reversible quarter-wave plate beam deflector,half-wave plate beam deflector,quarter-wave plate metalens,half-wave plate metalens.We verified the feasibility of the dual-function device by simulation,and explained that the method has a good contribution to the miniaturization and integration of functional devices.(3)We proposed a reflection filter based on silicon micro-disk.We propose a THz reflector based on Si micro-disk array,which is based on the electric dipole and magnetic dipole resonances of Si micro-disk to achieve 100% reflection in the terahertz range.At the same time,the frequency range of the designed reflector can be manipulated by varying the geometric sizes of the Si micro-disk,while the reflectioncan keep around 100%.Moreover,the operating frequency of the designed reflector can cover a wide range of 1.0~1.5THz.Additionally,the proposed reflector has a good adaptability for the incident incident angles(ranging from 0°to 25°).Besides,the frequency of reflector can be also operated with the splitting Si micro-disk arrays,where the presence of the splitting gap does not induce additional losses.