Study Of Graphene Light Absorption Theory And Detection Technology

As a new two-dimensional material,graphene has attracted more and more attention in the field of optoelectronics due to its excellent optical and electrical properties.Because graphene has the characteristics of ultra-high carrier mobility,wide spectral absorption range,large response bandwidth,it has important significance for the research and development of new photoelectric detection materials and devices.The absorption rate of monolayer graphene is only 2.3%,which restricts the development of graphene in optoelectronic devices.The enhancement of monolayer graphene and waveguide-integrated graphene structure is focused on in this paper.Based on the absorption enhancement of graphene,experiments on graphene photoelectric detection are carried out.Firstly,a metal-dielectric elliptical cavity array is designed to enhance the absorption of monolayer graphene.The classical LC circuit model is used to reveal the resonance relationship of the cavity mode,which ensures the accuracy of the simulation results.Meanwhile,the coupled harmonic oscillator model is used to reveal the mechanism of enhanced absorption.The effects of graphene nanoribbon filling factor and mobility parameters on absorption enhancement are investigated.Finally,A bandwidth of 6μm with an average broadband absorption rate of 78.8%is obtained for the monolayer graphene,which provides a new idea for the development of high-performance graphene photodetector in the mid-infrared spectral region.In order to apply the excellent electro-optical properties of graphene to the waveguide detection and promote the development of integrated optics,the graphene-integrated rectangular waveguide,ridge waveguide and slit waveguide are numerically simulated by finite element software.The influence of different types of waveguide size parameters on the absorption efficiency,absorption ratio and absorbance of graphene are discussed.The waveguide width,height and transmission length under the optimal case of graphene absorption are calculated.The graphene absorption coefficient is 0.1444 d B·μm^-1in the rectangular waveguide,0.1551 d B·μm^-1in the ridged waveguide and 0.2070 d B·μm^-1in the slit waveguide.This work will promote the application and development of graphene-integrated waveguide optoelectronic devices,and has certain reference value for the dimension design of graphene-integrated waveguide.Finally,the preparation of graphene film and its photoelectric detection performance are investigated experimentally in this paper.The wet transfer method of monolayer graphene is studied,and then the characterization of monolayer graphene including optical microscopy characterization and Raman spectroscopy characterization is carried out,which can be used to effectively determine the defects and the number of layers of graphene films.Based on the built detection system,the graphene surface absorption detection and graphene integrated rectangular waveguide detection research are carried out.The graphene detection chip is fabricated and tested.The surface detection responsivity reaches 0.13 A/W,in which the bolometric effect is the main detection mechanism.This work lays a foundation for the further research on high-performance graphene photodetectors.