Optical Filtering Properties And Structural Color Based On Dual-grating Nanocavity Metasurfaces

Structural color refers to the physical color generated by the interaction between incident light and microstructures.It is an ideal and sustainable color choice due to its stability and environmental friendliness.In recent years,researchers have shown that structural color can be tuned by controlling the shape,size,and distribution of the microstructure to adjust its resonant wavelength through extensive biomimetic studies of structural color in nature.With the rapid development of micro-nano science and manufacturing technology,researchers can now fabricate complex structures,such as nano photonic crystals and nano metal structures,on a micro-nano scale using micro-nano processing technology.By precisely controlling the structural parameters,researchers can display a wide range of colors.Due to the richness of the physical mechanism of interaction between micro-nano structures and incident light and the diversity of application requirements,research and application of artificial structural color or micro-nano structure-based filter devices are still in a rapid development stage.Ln this thesis,color filters based on dual-grating nanocavity structures that have high design flexibility,rich color and excellent polarization characteristics are proposed and investigated.The results of both theory and experiment demonstrate its potential applications in color filtering,full-color displays,anti-counterfeiting image and other fields.The main contents and contributions of this thesis are as follows:1.A transmission-type color filter based on a double metal grating nanocavity is proposed and demonstrated.The structure consists of a double metal-dielectric-metal(Ag-SiO2-Ag)cavities,where the dielectric layer is a grating structure,and a thin silver film covers the top and bottom of the dielectric grating,respectively,forming a dual cavity structure with a freely controllable short nanocavity and long nanocavity.The structure can generate different transmission colors when different polarization states of incident light are introduced.By precisely controlling the width ratio and the length of the long/short nanocavity,grating periods,and grating orientations,the transmission spectra under the transverse magnetic(TM)and the transverse electric(TE)polarized light can be freely adjusted.Furthermore,due to the joint action of localized surface plasmons resonance and nanocavity resonance,the strength of the two resonance modes can be adjusted by changing structural parameters such as the width ratio,thereby achieving unique absorption characteristics.Using this absorption characteristic,a single high-order resonance peak with a narrower peak width can be obtained,avoiding multiple high-order peaks produced by traditional nanocavity resonance modes,thus producing a purer color display than that in the traditional cavity resonance.2.Experimental fabrication and validation of the proposed dual-metal grating nanocavity transmission filter are conducted.Based on the proposed dual-metal grating nanocavity transmission filter,coating technology and electron beam exposure technology are employed to prepare different samples,testing and imaging setup to detect and validate the spectral and imaging properties of the prepared samples are established.Specifically,we verified the transmission colors and spectra under different polarization states for dual-metal grating nanocavity structures,and demonstrated the method for achieving high-order peaks using the absorption characteristics with different short cavity lengths.Full-color patterns with different grating aspect ratios,periods,and orientations of the dual gratings on a single substrate are also fabricated.Experimental results confirmed the validity of the theoretical design and methods,and demonstrated the potential applications of dual-metal grating nanocavities in areas such as color filtering,full-color displays,and anti-counterfeiting image.3.A polarization-independent reflective color filter based on a dual-nanocavity array was designed.The structure is composed of a two-dimensional(2D)metal-dielectric-metal(Ni-SiO2-Al)dual-cavity structure,where the SiO2 dielectric layer is a 2D grating.The top and bottom of the 2D dielectric grating are uniformly covered by metal Ni and metal Al films,respectively,forming a dual-cavity structure with controllable short and long cavities.By adopting a square unit cell structure and optimizing the cavity length and filling factor of the dual-cavity 2D structure,different reflective colors with polarization-independent characteristics can be effectively designed and manipulated.Theoretical calculation results show that the bandwidth of the reflective peak of the filter can be reduced by about 50%compared with the traditional F-P cavity structure,and the color gamut can be expanded by about 2.6 times compared to the traditional F-P cavity reflective color filter.The proposed structural device has important potential applications in color printing,display,and optical anti-counterfeiting.