By imparting local, space-variant phase changes on an incident electromagnetic wave, metasurfaces are capable of manipulating lights. These surfaces have been constructed from nanometallic optical antennas as well as high-index dielectric antennas. We introduce a unique scalable Fourier transform 4-f system that is applied to lithography. We demonstrate the experimental realization of a flexible Fresnel element, where pixelated one dimensional gratings with space-variant frequencies and orientations are assembled in low-index material as the UV resin on polyethyleneterephthalate (PET) substrate, achieving good concentration performance in the visible spectrum.
A reflective color filter based on the standing-wave resonance is proposed, incorporating an asymmetric cross-shaped aluminum grating on top, a sandwiched silicon nitride layer and an aluminum mirror at bottom. By varying the length of grating arms or the polarization of incident lights, reflective colors as cyan, magenta and yellow can be obtained conveniently. Specially, reflections show good angular tolerance up to 60° for transverse electric polarization, while they demonstrate high sensitivity to incident angles of transverse magnetic polarization. Furthermore, the black color can be realized in reflection by encoding four gratings into one pixel at the optical diffraction limit. The color filter proposed here has great potential in applications as reflective LCD, full color printing and anti-counterfeiting.
A reflective color filter showing polarization dependent is proposed, where on a SiO2 substrate, a Si-grating is embedded inside a dielectric Si3N4 overlay. By varying the period of the grating, cyan, magenta and yellow (CMY) colors are gained for the transverse electric (TE) polarized incidence. With the polarization of incident light changed from TE polarization to transverse magnetic (TM) polarization, the structure’s reflective color varies accordingly. Therefore, the proposed structure has application prospects in the field of anti-counterfeiting and color display.
A reflective color filter based on the micro-cavity incorporating a nanostructure is proposed, which consists of a nano-metallic grating, a dielectric layer and an aluminum (Al) film. By varying the duty cycle of the metallic grating, red, green and blue (RGB) colors can be obtained for the transverse electric (TE) polarized incidence, having a good angular tolerance up to 30°. While these structures show different colors for transverse magnetic (TM) polarized light, and the color difference caused by polarization changes with the duty cycle chosen in different range. Therefore, the proposed structure demonstrates distinct reflections with different duty cycles, which can be utilized for reflective color displays as well as anti-counterfeiting devices.
Color filters based on different Fabry-Perot structures are investigated extensively, and incident angle dependency is an important characteristic in practical applications. Here, we investigated a color filter incorporating a Fabry-Perot structure, discussing its reflective angular sensitivity related to refractive index of its dielectric material. By finite difference time domain(FDTD) theory, the refractive index of the dielectric material is found to influence the angular sensitivity greatly while the optical thickness keeps constant. The simulated results shows that the higher the dielectric layer’s refractive index is, the more angular insensitive of the reflection will be obtained and a good angular insensitive will achieved when the refractive index is larger than 2.1. Finally, samples with different dielectric layer are fabricated in experiment and the measured results verify influence of the refractive index of dielectric layer on the spectra angular sensitivity, which is helpful for the application of color filter in color display, image sensors and decoration.
A printable color filter based on the photonic micro-cavity incorporating a nanostructure is proposed, which consists of a nano-metallic grating, a dielectric layer and aluminum (Al) film. According to the resonance induced by different dielectric depths of the micro-cavity, two dielectric heights for the same resonant wavelength are chosen to form the grating heights relative to the Al film. With the contribution of the cavity resonance and the surface plasmon resonance, the proposed structure performs enhanced broadband filtering characteristics with good angular tolerance up to 48° compared to the one of the micro-cavity as well as the one of the metallic grating. Therefore, reflective filters for RGB colors are designed incorporating the proposed structure. Furthermore, for the proposed structure shows great polarization dependence even at normal incidence, it can also be utilized as an anticounterfeiting certificate.
We numerically and analytically report an ultra-broadband near perfect absorber based on one-dimensional metal-dielectric-metal grating at visible light for TM polarization. A unit cell of this design is composed of metal-dielectric-metal grating, where the bottom metallic layer and the upper metallic coating are separated from each other by the intermediate dielectric grating. The absorber exhibits an average absorption of over 90% in the range 400-700nm. Moreover, they remain very high over a wide range of incident angle up to 45°.The electromagnetic field distributions are investigated, which reveals that this broadband absorption behavior is ascribed to the combination of surface plasmon resonance and cavity resonance. Furthermore, impedance calculations were carried out to explain the absorption behavior. The ultra-broadband near-perfect angle-robust absorber can be a good candidate for many fascinating applications, including solar-energy harvesting as well as producing artificial colors on a large scale substrate.
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