Color-selective diffractive optical components based on composite multilayer structures including phase-change materials

We present a composite multilayer resonance structure for color-selective diffractive optical components in the visible region. The structure consists of stacked layers of indium tin oxide (ITO), a phase-change material... [ view full abstract ]

We present a composite multilayer resonance structure for color-selective diffractive optical components in the visible region. The structure consists of stacked layers of indium tin oxide (ITO), a phase-change material Ge₂Sb₂Te₅ (GST), and silicon dioxide (SiO₂) on an aluminum substrate. By printing binary spatial patterns on the imbedded GST layer using an ultraviolet laser patterning technique, color-selective diffractive properties with a moderate bandwidth can be obtained [1]. Figure 1(a) shows the design of the proposed structure, in which the dispersive profile of the first-order diffraction efficiency can be tuned by controlling the thickness of the SiO₂ layer.

To verify the proposed structure, numerical simulations are conducted to reveal the relationship between the thickness of the SiO₂ layer and the spectral diffraction efficiency for normally incident plane waves, as shown in Fig. 1(b). Based on this relationship, we fabricated a full-color computer-generated hologram (CGH) using a spatial multiplexing technique [2] capable of reconstructing holographic images with red, green, and blue light with wavelengths of 660, 532, and 473 nm, respectively. Accordingly, three SiO₂ thicknesses of d = 252, 390, and 150 nm were selected considering the relative diffraction efficiency at the selected wavelengths. The corresponding profiles are shown in Fig. 1(c). Figure 2 shows the fabricated full-color CGH and a zoomed-in image of the CGH. The printed CGH pattern has a pixel pitch of 2 μm, and a resolution of 16,384 × 16,384. During the CGH generation step, the right and left source images shown in Fig. 3(a) are positioned at distances of d = 0.12 and 0.15 m from the hologram plane, respectively. Figure 3(b) shows experimentally measured reconstruction images at two different focal planes, from which sharply focused “ETRI RGB” and a checkered pattern can be observed at the intended distances. The results demonstrate the effectiveness of the proposed method.

This work was supported by 'The Cross-Ministry Giga KOREA Project' grant from the Ministry of Science, ICT, and Future Planning, Korea [GK17D0100].

[1] S.-Y. Lee et al., Scientific Reports 7, 41152 (2017)

[2] Y. Tsuchiyama et al., Opt. Express 25, 2016-2030 (2017)