The development of digital holography is anticipated for the viewing of 3D images by reconstructing both the amplitude and phase information of the object. Compared to analog holograms written by a laser interference, digital hologram technology has the potential to realize a moving 3D image using a spatial light modulator. However, to ensure a high-resolution 3D image with a large viewing angle, the hologram panel requires a near-wavelength scale pixel pitch with a sufficient large numbers of pixels. In this manuscript, we demonstrate a digital hologram panel based on a chalcogenide phase-change material (PCM) which has a pixel pitch of 1 μm and a panel size of 1.6 × 1.6 cm2. A thin film of PCM encapsulated by dielectric layers can be used for the hologram panel by means of excimer laser lithography. By tuning the thicknesses of upper and lower dielectric layers, a color-selective diffraction panel is demonstrated since a thin film resonance caused by dielectric can affect to the absorption and diffraction spectrum of the proposed hologram panel. We also show reflection color of a small active region (1 μm × 4 μm) made by ultra-thin PCM layer can be electrically changed.

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In this paper, we propose a scheme for designing a tunable pixel layer based on a Ge2Sb2Te5 (GST) alloy thin film. We show that the phase change of GST can significantly affect the reflection characteristic when the GST film is embedded into a dielectric encapsulation layer. We investigate the appropriate positions of the GST film within the dielectric layer for high diffraction efficiency, and we prove that they are antinodes of Fabry–Perot resonance inside the dielectric layer. Using the proposed scheme, we can increase the diffraction efficiency by about ten times compared to a bare GST film pixel, and 80 times for the first‐to‐zeroth‐order diffraction power ratio. We show that the proposed scheme can be designed alternatively for a broadband or wavelength‐selective type by tuning the dielectric thickness, and we discuss a multi‐phase example with a double‐stack structure.

This article describes a new electrochromic device (ECD) designed to achieve improved black color and long‐term bistability. We achieved these improvements by fabricating a double‐layered nanostructure of two different electrochromic materials stacked in layers on a single electrode. The fabricated ECD maintains 90% of the light transmittance of the colored state even after 1 h if powered off in the colored state. To achieve an improved black, green and blue viologens were successively immobilized in the bottom and top layers of materials on an electrode. The green viologens are initially colored at low voltage, and the purple viologens become colored when the voltage increases. This is because the reduction potential of the green viologens is less than that of purple viologens. Finally, an improved black color is obtained through a mixture of the two colors.