Study Of Surface Plasmon Lattice Resonance In One-Dimensional Grating And Its Integrated Application With Two-Dimensional Materials

Surface plasmon（SP）,the collective electron oscillation that exist at the metal interface excited by electromagnetic waves,has promising applications because of its strong local electric field enhancement and many exciting optical phenomena.However,due to the inherent loss in metals,SP artificial metasurfaces often exhibits a very low quality（Q）factor（Q<10）,which strongly limits their application in biosensing and light modulation.When the wavelength is close to its Rayleigh anomaly（RA）wavelength,the metallic nanoparticles arranged with a periodic array can excite a novel SP resonance,namely surface plasmon lattice resonance（SPLR）.And a sharp narrow linewidth occurs in the spectrum.However,due to the strong angular dispersion,SPLR excitation requires high spatial coherence of light using a low numerical aperture（NA）objective to ensure its high Q factor.When focused light beams is used by high NA objectives,the collimation of incident light will be damaged with the broaden linewidth of SPLR,and the Q factor will be also correspondingly decreased.However,in most cases,it is necessary to use high NA focused light to further enhance the intensity of light field and the efficiency of signal collection.However,high performance SPLR can not be excited under focused light,which also hinders its application in miniaturization and compact integrated devices.In addition,due to the unique electronic and optical properties,two-dimensional（2D）materials have attracted lots of attention.However,due to its extremely short light-matter interaction distance and difficulty in large areas,high NA objective are indispensable for enhancing the interaction between 2D materials and light,which has also led to the stagnation of the research on SPLR metasurfaces integrated with 2D materials.To solve this issue,this dissertation combines the conversion of various optical modes within 1D grating metasurface,and theoretically proposes a SPLR metasurface that can preserve high Q resonance under focused light beam,and verifies its results in experiments.This property can greatly expand the application of SPLR metasurfaces in the field of spatial light and.Ultimately,stronger light-matter interactions can be achieved and the compatibility of integrated devices can be increased.And then,the metasurface is integrated with 2D materials and its applications in second harmonic generation（SHG）and photodetection are also studied.Utilizing the property of the narrow-band resonance under the high NA objective,the proposed metasurface can enhance the interaction between light and 2D materials,and it also improves the light modulation ability of SP resonance to 2D material.This also makes the 2D material-integrated SPLR metasurface exhibit different properties in SHG and photodetection compared with conventional 2D material-integrated SP metasurfaces.The major results are summarized below:1.Firstly,through theoretical simulation calculations,1D grating SPLR metasurface that can preserve the Q factor under focused beams is proposed.According to the analysis of angle-resolved spectra,this property is caused by the optical mode transition of the metasurface under oblique incident light.After that,the proposed SPLR metasurface and the 2D SPLR metasurface for comparison are prepared by micro-nano processing,and their resonance spectra are characterized experimentally by self-built optical system.When the low NA objective is replaced with a high NA objective,the full width at half peak（FWHM）of the 1D SPLR metasurface only increases from 3.2 nm to 3.9 nm,and the corresponding Q factor decreases from 484 to 393.However,the resonance linewidth of 2D SPLR metasurface is significantly broadened,and the Q factor also reduce to a quarter of the value measured using a low NA objective.Compared with various SPLR metasurfaces reported in recent years,when the objective with NA=0.4 is used,its Q factor is about one order of magnitude higher than other SPLR metasurfaces.2.Based on the above property,under focused light beams,the 1D grating metasurface can enhance the interaction of light with 2D materials while preserving its high Q-factor.And then,the proposed metasurface is integrated with 2D GaSe with high second-order nonlinearity,and its absorption spectra and the SHG enhancement are also studied.Due to the presence of 2D GaSe,the angular dispersion has been slightly changed,the light absorption increases to over 90%measured by a NA=0.4 objective.In addition,when SPLR is excited,the integrated metasurface with 2D GaSe with the thickness of 15and 30.9 nm show a SHG enhancement about 11 and 30 times,respectively.Moreover,when 2D GaSe is integrated with SPLR metasurface,SHG polarization of 2D GaSe will change from being controlled by crystals to being dominated by SPLR.In addition,when the thickness of 2D GaSe is 30.9 nm,SHG spectrum of the integrated metasurface also shows an ultranarrow FWHM of 1.26 nm,and this is impossible for SP metasurface with low Q factor.3.Sandwiched 2D MoS₂ between the 1D grating and the underlying Au film,a hot electron detector based on SPLR and gap resonance is proposed.Because the proposed detector is manipulated by multiple resonance modes,it displays a photo response spectrum that is not consistent with that of ordinary hot electron detectors.As the absorption increases,the photocurrent decreases significantly.In addition,the polarization of photo response also shows different functional relations at different wavelengths.This phenomenon has been theoretically explained using the finite-difference time-domain method.Such polarization characteristic will also expand the application of hot electron detectors in fields,such as wavelength division multiplexing,polarization multiplexing,and encrypted communication.Finally,by controlling the thickness of MoS₂ and the adhesive layer between the grating and MoS₂,the photo response spectra and polarization can also be effectively manipulated.