Forming And Tuning The SPP Optical Field In Graphene-nanocavity And Its Application In Super-resolution Imaging

In last few decades,the great progress in optical imaging has led to a profound impact on biological living cells research.Various methods were developed to improve the optical imaging resolutions including stimulated emission depletion microscopy(STED),near-field scanning optical microscopy(NSOM),and structured illumination microscopy(SIM),etc.Among these methods,more and more attentions are being paid to SIM for it can achieve high resolution optical imaging at wide-field.However,the spatial resolution of SIM is theoretically limited to 100 nm.More recently,plasmonic structured illumination microscopy(PSIM)was proposed to further improve the resolution by taking advantage the higher wavevector of surface plasmons.Normally,noble metal is used for generating surface plasmons.However,the main problem of noble metals is that the loss is rather high so that the coupling efficiency as well as the propagation length of surface plasmons is limited.Graphene,as a two-dimensional(2D)material formed by carbon atoms in honeycomb arrangement is only about 0.34 nm thick and has drawn extensive attentions in recent years.More recently,it was reported that strong coupling of light with electrons in graphene,i.e.graphene plasmons,at middle-infrared and THz wavebands can be realized,and thus magnetic(TM)polarized surface plasmons can be stimulated and excited.In comparison with conventional plasmons excited in noble metals,graphene plasmons have stronger ability to confine optical field with lower loss.Moreover,it can be tuned by gating or doping to make active devices in a broadband from middle-infrared to THz due to its changable conductivity.Therefore,there is the possibility to incorporate graphene plasmons in PSIM method to further improve the optical imaging resolution.In this work,firstly,we propose a so called graphene nanocavity on meta-surface(GNMS)structure model by intelligently integrating graphene nanocavity with meta-surface for super-resolution imaging in PSIM method.The dispersion relationship of the model is firstly discussed and then followed by simulating the structure by employing FDTD method to obtain SPP in the nanocavity.It is found that the plasmonic interference pattern generated on graphene has a period of 52 nm for a 7 ?m incident light wavelength.The field is promoted about 134 folds,which noble metal cannot reach.What's more,one adapted the method of analytical and simulation demonstration to understand the nanocanvity better,and explored the influence and tuning of relevant parameters in the structure such as material,period,duty cycle and the thickness of meta-surface.The tuning of the thickness of water film,chemistry of graphene were also discussed to figure out the property of graphene plasmons.To satisfy the destination of applicant of the model in super-resolution,we simulated and calculate the diffracted limit and find out they are 25 nm and 26 nm respectively,which mean 100-time resolution is reached.Overall,the model we researched will contribute to the development in biological super-resolution applicants.