Structural Color Filters And The Applications In CMOS Image Sensors And Colorimetric Sensors

Color is one of the most important attributions of human visual perception. Instead of the black and white screens, color displays dominate current consumer electronics market giving us a better visual experience. Nowadays nearly all color displays such as liquid crystal screens rely on the dye-doped color filters that show colors based on wavelength-selective light absorption. These dye-doped filters are also called chemical color filters. However dye-doped color filters cannot withstand high temperature or irradiation of ultraviolet radiation resulting in the color fading over time seriously. Furthermore, these material based color filters require multi-step aligned photolithograph process with increased cost and difficulties. Recently, scientists on color filters have benefited from natural biological phenomena, such as the hue from butterfly wings, and revealed a new color filtering mechanism, namely physical color, or structural color. Structural color coming from the interaction between light and nanostructure is attributed to light interference, diffraction, scattering, etc. This study of structural color can overcome the shortcomings of conventional chemical color, and it provides simple fabrication process, compactness, robust stability, environmental friendliness. The large free degree of design offers multiple functions and novel applications of structural color filters.In this paper, we study the fundamental physics of surface plasmon resonance and guide mode resonance and investigate the associated color filtering properties. Based on these, we develop the applications in CMOS image sensors and colorimetric sensors, which may provide a new route for developing next generation high-resolution image sensors and high-sensitivity portable colorimetric sensors.This paper consists of five chapters.The first chapter introduces the funding project information, surface plasmon resonane; guide mode resonance; CIE three primary color and the main contents of the paper.The second chapter investigate in detail the applications of the structural color filters based on surface plasmon resonance in CMOS image sensor, where structure color filters are designed to replace conventional chemical color filters. The spatial optical crosstalk are investigated in details and it is found that by integrating structure color filters in the metal layer of standard CMOS chips, lower spatial optical crosstalk can be achieved and 500 nm of single pixel also can be expected.The third chapter mainly investigate the applications of the structural color filters based on surface plasmon resonance in colorimetric refractive index sensor. And it predicts a visible color difference of 4.17 a refractive index difference as small as 0.01. In experiment using metal-coated PS spheres, a sensitivity of 475nm/RIU are obtained. A color change from bright green to yel ow green are observed after dropping ethanol on the sample.The fourth chapter describes the work on the applications of structural color filters based on guide mode resonance in two types of colorimetric sensors. One is colorimetric refractive index sensor, multiple guided- mode resonance structure color filters have been studied to improve the senstivity. And it theoretically shows a visible color difference of 3.33 a refractive index difference as small as 0.01. The other is colorimetric polarization sensor, Polarization characteristics of asymmetrical dielectric grating based on guide mode resonance is applied to design colorimetric sensor. When polarization angle changed within the range of 0-90 degrees, the maximum value of color difference reaches 62, and the mean value of color difference is 3.1 for a variation of 5 degrees polarization angle.The fifth chapter is the summary and outlook of the paper. The main content and the innovations of the work on structure color filters and the applications in CMOS image sensor and colorimetric sensor has been summarized. The current work has clarified the feasibility and effectiveness of structure color filters in the applications in CMOS image sensor and colorimetric sensor. The next step is to further enhance the optical efficiency, angle sensitivity and light field confinement of structure color filters and develop advanced fabrication technique of nanostructure, which is believed to promote the practical application of structure color filters.