Switchable Holographic Device Using Electrochemical Method

The holographic display based on digital technology has attracted much attention as a next generation realistic display. Spatial light moudulator (SLM) is considered as a key element to enable such digital holography... [ view full abstract ]

The holographic display based on digital technology has attracted much attention as a next generation realistic display. Spatial light moudulator (SLM) is considered as a key element to enable such digital holography technology. However, pitch scale down for securing wide viewing angle has become a big technical issue in the development of SLM. In this study, we propose a novel device using reversible electrodeposition to overcome the limitation of the pitch scale down which has been recognized as the limit of the voltage driving device such as liquid crystal display.

The reversible electrodeposition technology is a technology that reversibly deposits or removes Ag on the electrode surface by application of an electric field. We propose a new device structure that can make hologram image using reversible electrodeposition technology.

Figure 1 shows the structure of the proposed device. The device consists of a lower mirror, a lower ITO electrode, an electrolyte, a WO₃ counter electrode, and an upper ITO electrode. Ag can be deposited or erased on the surface of the lower ITO electrode by application of an electric field. The left picture shows the state where Ag is erased, and the right picture shows the state where Ag is deposited. In these two cases, the reflective layer of the incident light changes. When Ag is not deposited, the primary reflection occurs in the lower mirror layer, but when Ag is deposited, a reflection occurs in the deposited Ag layer. Therefore, the light reflected from these two cases has a phase difference due to the thickness of the ITO layer and the thickness of the deposited Ag.

Figure 2 shows the simulation result of the complex reflectance of the reflected light, which is characterized by phase modulation. Figure 3 shows the hologram-driven image of the device with 1μm pixel pitch. The device is capable of on / off driving and it is possible to realize excellent hologram image.

Acknowledgment

This work was supported by Institute for Information & communications Technology Promotion(IITP) grant funded by the Korea government(MSIT) (No.2017-0-00065, The core technology development of high performance materials and devices for volumetric display)