Research On Two-dimensional Color Filters Based On Surface Plasmon Polaritons

Color filters are key components for modern optical instruments.With the development of society and progress of technology,the traditional color filters which mainly employ organic dyes,however,cannot satisfy the growing demand,especially in the field of color image with ultra-high resolution.Restricted by the optical diffraction limit,the unit size of traditional color filters cannot be further reduced,which hinders the development of nanoscale pixel units and integrated circuits.Based on the principle of surface plasmon polaritons(SPPs),novel color filters with simple cost-effective architecture appear.As its color can be modified by just changing its own nanostructure,which fundamentally breaks through the limitation of optical diffraction,the new color filter has an extraordinary meaning in the development of color filters.Although the color filters developed on the basis of SPPs are diverse,there are still flaws.The EOT-based color filters have low transmission efficiency.While the emerging ELT-based color filters composed of one-dimensional gratings overcome the problem of low transmission,their behaviors are related to the polarization of the incident light.These defects seriously affect their practical application.Under this circumstance,we design a new type of two-dimensional ELT-based color filters on ultra-thin silver film and make both theoretical and experimental research.In this paper,the principle and characteristics of surface plasmon polaritons are firstly introduced,including its dispersion relation,skin depth and propagation length.Then we elaborate the methods of exciting SPPs by incident light.We make an overview of the microstructure processing,such as film preparation and micro-nanostructure fabrication techniques,and also make a detailed analysis of their advantages and disadvantages.Then,we make a series of modeling calculations and finally design a novel type of color filters with two-dimensional circle hole array on ultra-thin silver film.The model not only has high transmission efficiency,but also has nothing to do with the polarization of incident light.The Finite-Difference Time-Domain software FDTD Solutions is used to simulate the effect of model parameters,such as,thickness of the material,the period and the duty cycle of the circle hole array.Based on the detailed analysis and experimental results,the tuning method of color is put forward,and the physical mechanism of this phenomenon is clarified.In order to further realize color filters with both high transmission and high purity,this paper,based on color filters with two-dimensional circle hole array on the ultra-thin silver film,further explores the optimization and proposes a new method to improve color purity.By reasonably changing the arrangement of the hole array,the method can not only effectively improve the color purity,but also maintain the advantages of the original high transmission.Based on the simulation results of the system and a series of sample test data,the empirical formula from the expected color to the preparation parameters of color filters mentioned above is given.By deriving the SPPs matching wavelength formula of the two-dimensional circle hole array with displacement,we explain the physical mechanism of color control.By analyzing the characteristics of the traditional preparation method and their existing limitations,this paper based on X-ray interference lithography(XIL)presents a new efficient method for preparing the two-dimensional array color filters in large scale.This method has high exposure precision,large single exposure area and spends only a short time.By designing and adding an order sorting aperture,this method can effectively avoid affection of the zero-order light.And then with the corresponding movement of the sample stage and the shutter,it theoretically can achieve perfect stitching of single exposure area.On this basis,this paper proposes a new method to control the color only by changing the duty cycle without changing the period,which greatly improves the utilization efficiency of the mask,reduces the cost in production and make XIL method more practical.Finally,the research results and innovations of this paper are summarized as follows:A kind of color filter model of two-dimensional circle hole array on ultra-thin silver film is proposed.It has high transmission and importantly,it's polarization-independent.The theoretical research of the system is carried out to establish a complete mathematical model.A new method of adjusting the color purity of color filter model mentioned above is proposed,this method can tune the color purity without changing the transmission of the filter.Then the guiding formula from the expected color to the filter parameters is summarized.The research on the preparation and test method is carried out,and a four-grating interference stitching method based on XIL optical path is proposed to fabricate efficiently a two-dimensional array color filter in large scale.In addition,we point out some problems that need to be solved further in our work,and give some advices on the future research in this field.