A joint research team led by Professor Junsuk Rho (ME and CE) and Prof. Young-Ki Kim (CE) developed an ultracompact holographic display that responds to external stimuli. The team produced such material by applying the stimuli-responsiveness of liquid crystals (LCs) to metamaterials, which is also known as “the material of dreams”.
Metasurfaces have been an active field of research due to their potential to enable futuristic displays such as virtual reality and 3D holographic displays. However, the optical properties of devices based on metasurfaces cannot be changed after production, and consequently, the field was limited to the production of devices that can only express the single initially programmed image.
Therefore, the research team designed metamaterials integrated with LCs that can easily change their optical properties in response to external stimuli. The team attached specifically designed LC-based light modulators to metasurfaces to produce stimuli-responsive dynamic displays. Depending on the LC material and the geometrical designs of the LC modulators, the displays were capable of responding to various external stimuli such as finger touches (surface pressure), voltage, or heat.
For example, when a voltage-responsive LC was used, the holographic image rapidly changed within a few milliseconds in response to the voltage of 0.8V and 1V. Also, a device incorporating a temperature-responsive LC switched holographic images above the temperature of 47°C. Moreover, a metahologram designed to respond to pressure quickly changed holographic images with only a light finger touch between 10 kPa and 0.1 MPa. In particular, very clear holographic images were produced within the range of visible light with wavelengths of 450 nm to 700 nm. Meanwhile, the team plans to continue its research to incorporate the newly developed devices into sensors that detect microorganisms or toxic chemicals.
The newly developed ultracompact metaholograms are expected to act as a catalyst in advancing various technologies, including video playback optical devices, temperature-sensitive hologram sensors, and futuristic interactive/haptic holograms. The research was funded by the Ministry of Science and ICT, the National Research Foundation of Korea, and LG display. The study was published on the front page of the Nov. 11 issue of the international journal, Advanced Materials.