OLED illuminated metasurfaces for holographic image projection.

Organic light-emitting diodes (OLEDs) are thin film optoelectronic devices that feature simple fabrication, light weight and broad tunability, which makes them widely used in mobile phone and TV displays. As a flat and surface-emitting light source, OLEDs are also used in emerging applications such as optical wireless communications, biophotonics and sensing, where the ability to integrate with other technologies makes them good candidates to realise miniaturised photonic platforms. Control of the OLED far-field emission is increasingly important for both displays and these emerging applications. At present, however, studies mainly focus on tuning the electroluminescence (EL) spectrum and emission directionality. Fine-tuning of the far-field emission is particularly challenging and is limited by the low spatial coherence of OLEDs. In this work, we show that it is possible for a single OLED to project a high-resolution image when combined with a holographic metasurface as a compact projection system. The metasurface-OLED projector allows us to directly manipulate the OLED far-field emission and display holographic images on a screen. Here, we further show how the projected image quality relates to the spatial coherence length and the spectrum of the OLED. We believe our demonstration provides a path towards a miniaturised and highly integrated metasurface display.