Research On The Manipulation Of Optical Property In Graphene-based Plasmonic Device

The development of science and technology make the integrated degree of electronic chips increased rapidly.However,it is hardly to improve the chip integrated degree in essence according to the prediction of Moore's Law.There are urgent requirements for researchers to seek some other methods that can improve the performance of electronic devices effectively.Compared with electrons,photons possess more faster speed,higher capacity and stronger anti-noise ability.Using photonics devices to replace electronic device which has become a basic research topic nowadays.On the other hand,through exciting the surface plasmon polaritions(SPPs)on metamaterials or metasurface,we can achieve a wide range of optical applications for developing future integrated optical circuit.Nevertheless,traditional metamaterials are constructed by metal and lack active control ability,which greatly limits its' application.To solve this problem,several tunable microstructure devices are designed by combining the characteristics of metal surface plasmons with the novel two-dimensional material of graphene,both of which may provide some designed schemes for the future development of integrated optics.The main contents include:1.Based on the tunability of graphene,we propose a graphene-based plasmonic unidirectional coupler,which is constructed by an asymmetric metal nanoantenna pairs covering with the graphene hybrid waveguide.By using metal nanoantenna,we can excite the SPPs on metal surface,and the corresponding radiation phase of asymmetric metal nanoantenna pairs can be controlled by the graphene.On the basics of these,we can realize the SPPs unidirectional propagation through applying a single voltage.Compared to previous reports,we designed structure with the advantages of small size,high extinction ratio(?2600),broadband tunable(wavelength range 6.3~7.5 ?m)and easy integration.It will play an important role in future photonic integration and optoelectronics.2.We propose a graphene-based plasmonic narrowband mid-frared absorber,which is composed of a tapered metal grating coupling with graphene ribbons arrays.At incident wavelength of 7.86 ?m,the 100% perfect absorption can be achieved,and the corresponding physical mechanism is revealed by calculating the field distribution.According to the electric field distribution,the perfect absorption is caused by the coupling of magnetic resonance and graphene plasmonic resonance.Besides,the device can also tune the absorption bandwidth by control Fermi energy level of graphene.Our proposed device can overcome the physical bottleneck that the mid-infrared graphene has smaller absorption due to its own intraband transitions,and provides the possibility for designing graphene photodetectors,modulators and sensors in the mid-infrared band.3.Based on the above studies,we proposed a graphene metasurface structure which partly filled dielectric in metal groove.Utilizing the Rabi splitting caused by strongly coupled between plasmonic resonance in graphene ribbions and magnetic resonance in the gratings cavities,we can achieve a broadband graphene-based SPPs perfect absorber.By tuning it's relevant geometry parameters and Fermi energy,the bandwidth of the structure can be tuned,so as to achieve the broadband and high-efficient graphene photodetectors and modulators,and it also makes the possible to implement integrated optical circuit in the future.