Researchers at the University of St Andrews have developed an OLED which can project a high-resolution image when combined with a ‘holographic’ metasurface.
Creating a compact projection system, the researchers created a metasurface-OLED projector which allows them to directly manipulate the OLED far-field emission and display ‘holographic’ images on screen.
The researchers believe that this demonstration will provide a path towards a miniaturised and integrated metasurface display
The setup consists of a ‘holographic’ metasurface, a bandpass filter, and an OLED. The metasurface used in this design was designed for coherent light sources, with the researchers manipulating the configuration of the OLED-metasurface system, enhancing the degree of spatial coherence to allow the holographic metasurface to directly modulate the unpolarised OLED emission, projecting a ‘holographic’ image onto a screen.
To project an image, the researchers designed an OLED with high brightness and long operational lifetime, with a device stack that was thermally evaporated on a silicon substrate using a top-emitting configuration.
Creating a ‘holographic’ image, the researchers designed a phase-only ‘holographic’ metasurface, working in transmission with each meta-atom functioning as a cylindrical waveguide.
The ‘hologram’ had 1667 x 1667 pixels of a 300 x 300nm size, with a ‘holographic’ image of 333 x 333 pixels.
Photo credit: University of St Andrews. Concept view (bottom left) of the proposed OLED illuminated holographic image projection system, together with three holographic images recorded under OLED illumination with different spatial coherence. The OLED was placed at various distance (top left: 3 cm, top right: 5 cm and bottom right: 6 cm) away from the metasurface