Researchers have developed a new approach to multicolor holography that could be used to make 3D color displays for augmented reality glasses, smartphones or heads-up displays without any bulky optical components. Researchers from Duke University, USA encoded a multicolor image onto a 300-by-300 micron hologram in a 2D waveguide structure, a very thin structure that guides light. The computer-generated hologram produces complex multicolor holographic images when the grating coupler is illuminated by red, green and blue light. The new fabrication method encodes holograms in a material that is compatible with integrated photonics technology. This means that the holographic devices are easy to mass manufacture with the same fabrication methods used to make computer chips.
The hologram producing elements could be incorporated into tiny chip-based devices that also house the light sources required to create the 3D images. The new multicolor holography technique is based on computer-generated holograms. Unlike traditional holography, which requires a physical object and laser beams to create the interference pattern necessary to form a holographic image, computer-generated holography generates interference patterns digitally. Computer generated holograms provide high-resolution 3D images, but it has proven difficult to create them in more than one color. The Duke team overcame this challenge by fabricating a grating and a binary hologram in a waveguide made of a light-sensitive material known as photoresist. They developed a way to integrate the interference patterns for red, green and blue into a single binary hologram pattern.