Fabrication And Optical Modulation Characteristics Of Graphene All-optical Modulator

Optical modulator is an indispensable essential device in photonics and optoelectronics,which has been widely used in the fields of optical interconnection,biology,medical treatment,environmental monitoring and safety monitoring.As existing and emerging technologies increasingly demands on high-speed,compact and broadband optical modulators,high-performance optical modulation solutions are becoming indispensable.The recently realization that two-dimensional layered material graphene could perform light modulation with excellent photoelectric properties has prompted intense research and significant advances,paving the way for realistic applications.In view of the shortcomings and gaps in the current optical modulation technology,this paper mainly studies the optical modulation of graphene combined with waveguide and the optical modulation of graphene in the spatial light field.The research can be summarized as follows:?1?The characteristics of graphene coated microfiber?GMF?waveguides in passive Q-switching and all-optical amplitude modulation were studied.Firstly,polydimethylsiloxane?PDMS?was used to transfer the graphene film to the cone region of the microfiber.Then the saturable absorber of the GMF all-optical modulator was placed in a 1.5?m erbium-doped fiber laser to achieve passive Q-switching.Finally,an all-optical modulation system for 980 nm pump light to modulate 1550 nm signal light was built,achieving a modulation rate of up to 50 k Hz and a modulation depth of 3.82 d B.?2?The characteristics of reduced graphene oxide deposited D-shaped fiber?RGODF?waveguides in terms of all-optical amplitude modulation were studied.Firstly,a convenient and controllable evanescent field-induced deposition method was used to cover the polished region of the D-shaped fiber with redox graphene.Then,we optimized the existing all-optical modulation system,and added polarization controllers to the pump and signal optical paths.By changing the polarization state,the interaction between graphene and D-shaped fiber can be changed,thereby achieving an 8 d B modulation depth.In addition,this modulator has strong mechanical stability,ease of fabrication,low cost and compatibility with optical fiber systems,which means it has great potential in photonics applications such as all-optical switch and all-optical communications.?3?We studied broadband all-optical spatial light modulation and switch based on the nonlinear optical property of graphene.We firstly measured the nonlinear refractive coefficient of the single-layer graphene in the order of10^-11 m² W by spatial self-phase modulation method.Taking use of the large optical nonlinearity and the broad linear absorption band of graphene,we demonstrated the ability of graphene in transforming the Gaussian beams into hollow beams in a broad wavelength range?405-900 nm?.Finally,we realized all-optical switch both in-phase and out-of-phase in one system.The experimental results were well explained by the nonlinear optical effect?Kerr effect and saturation absorption?and the bubble scattering effect.This work suggests that graphene is a very promising nonlinear medium and can be applied to the broadband all-optical modulation and also provides useful information in understanding the mechanism of graphene in interacting with the lights.