Plasmonic Enhancement And Polarization Control On The Optical Response Of 2D GaSe Layers

Two-dimensional materials have attracted wide attention and great research enthusiasm for their unique structure and excellent physical properties.However,their ultra-thin thickness results in poor light absorption and low quantum efficiency,which inevitably limits their use in photonic devices.Effectively enhancing and flexibly controlling the optical response of two-dimensional materials is extremely important to meet practical application needs.Therefore,in the work of this paper,we construct a hybrid structure of two-dimensional materials and metal nano-array to form surface plasmon resonance(SPR)to achieve enhanced and polarization controllable optical absorption of two-dimensional material.The specific work is divided into the following aspects:(1)The hybrid structure of 2D GaSe layers and Ag nanoprism array is designed.The geometric parameters(prism edge length,thickness,spatial relative position)of the Ag nanoprism are optimized by FDTD method to maximize the the extinction response of the hybrid structure in the band edge possible edge 580-630nm of the GaSe material.Futhermore,we designed a special Ag grating array structure to realize the polarization controllable plasmonic-enhancement on the optical response of 2D GaSe layers.The geometric parameters(grating period,grating thickness,prism side length)of the grating structure are optimized by the FDTD method to maximize the extinction polarization of the GaSe/Ag grating hybrid structure at the GaSe band edge.(2)With the guidance of theoretical calculation,a large-area high-quality periodic hexagonal array of prismatic prisms was fabricated on the mechanically stripped GaSe thin layer by PS ball mask method.The Raman spectrum and the photoluminescence(PL)spectrum of the formed hybrid structure show a uniform and significantly enhanced signal,and the enhancement factor increases as the GaSe thickness decreases.We explore the mechanism of optical enhancement by simulating electric field coupling and interfacial interactions in the hybr:id structures.The near-field distribution indicates that three surface plasmon resonance modes are formed in the dielectric environment that changes dramatically in the limited space between GaSe,Ag nanoprisms,and the surrounding environment.At the same time,the differential surface charge density and charge transfer analysis reveal that the charge accumulation at the GaSe-Ag interface enhances the interaction between the GaSe thin layer and the incident light,forms optical resonance enhancement.Moreover,the spatial localization of plasmons and the good penetration of the laser in the GaSe layers lead to a thickness-dependent optical enhancement effect on GaSe films.(3)A large-area patterned grating array structure with Ag nano-prisms unit was successfully fabricated on the mechanically stripped GaSe thin layer.In the PL spectrum of the Ag grating/GaSe hybrid structure,the polarization response with a maximum polarizability of 15.2%was successfully observed,and the polarization controllable optical anisotropic properties of GaSe were realized.The above results provide an effective way to detect the optical signals of extremely thin two-dimensional materials,demonstrating the effective regulation of the polarization and photoelectric properties of two-dimensional materials by plasmon resonance enhancement,which provides an important reference for the polarization application of two-dimensional materials.