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.
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