Research On THz Micro-nano Optical Device Based On Graphene

Metamaterials have attracted a lot of attention in the past decade,because of its remarkable properties in electronics and photonics.Metamaterials are widely applied in invisible cloak,negative refractive devices,metalens and so on.So far,most metasurfaces rely on accurately designed metallic nanostructures.At visible and near infrared frequencies,varied geometric metallic nanostructures with strong resonance for surface plasmon act as local antennas in frequency selective surfaces.However,the plasmonic response of metals gradually reduced as approaching mid-infrared or lower frequencies.The response characteristic of the metallic nanostructures is fixed and can't be tuned,as long as the device is completed.While,the substitute for metal is obtained with the emergence of graphene.The nanostructures based on graphene have strong plasmon response at far infrared and terahertz frequencies.And the electromagnetic characteristic of graphene can be tuned by doping or by adjusting the bias voltage.Hence,further researching of graphene is significant for the development of tunable optoelectronic devices at far infrared and terahertz frequencies.In this paper,we illustrated the electromagnetic characteristic of graphene,and analyzed the conductivity,the permittivity and the tunability of graphene;The structures based on graphene have been modeled and simulated utilizing FEM(Finite Element Method),to study the plasmon response of graphene devices and the phase modulation effect of the field distribution;The graphene has been transferred to the target substrate utilizing the method of wet transfer and imaged according to design requirement utilizing the SEM/FIB system;The experimental results are tested by microscope,Raman spectrometer and SEM;We designed and optimized the polarized beam splitter and the tunable broadband absorber based on graphene nanostructures.The main content and innovation include the following points:(1)The graphene ribbons only respond to polarized light.So we proposed to divide the graphene into rectangular.The rectangle structures response to both TE and TM mode at the same time.The beam splitting of TE and TM mode could be realized by reasonably arranging the graphene unit.(2)When we analyze the phase modulation caused by graphene ribbons,we found that,the modulator can be converted to absorber by expanding the period of the structure.We proposed a multiple layers absorber,which have tunable broadband absorption spectrum.The absorption windows of this absorber can dynamically tuned by adjusting the bias voltage.