Bragg Polarization Grating Technical Details

Technical Details

SPECIFICATIONS

AR/VR Gratings

  • Diffraction of single order only (+1st order, RHC)
  • 0th order (LHC) is undiffracted
  • Diffracted order is always orthogonal to input
  • RHC -> LHC
  • Efficiency:  Up to 90% diffraction efficiency through a waveguide
  • Max Efficiency for single grating: Near 99%
  • Field of View:
    • >80° in direction of diffraction
    • >100° diagional
  • Requires very high index waveguide
  • Subwavelength Grating Periods for VIS and IR
  • Minimum Grating Period: <300nm
  • Grating Thickness: ~2um
  • Can be tuned for Narrow or Wideband use
  • Size: up to 300 x 300mm sq; round samples custom

Telecom Blazed Gratings

  • >90% Efficiency
  • Transmissive
  • Can be made reflective with reflective substrate

BENEFITS

AR/VR

BPGs are the only technology for holographic waveguides that give unparalleled efficiency, coupled with single order and single polarization diffraction, that operates over an extraordinary wide field of view (FOV). These gratings can also be implemented with an efficiency gradient that helps with color and brightness uniformity. These aspects make the BPG ideal for use in augmented reality. One polarization can be used with high efficiency over a large FOV to convey the overlayed information and the other polarization (external view from the outside world) can come through without distortion.

Telecom

  • Thinner
  • Higher efficiency
  • Large angle of operation
  • Can be tuned to operate over full band with high efficiency

Any desired angle of incidence (e.g., in=0۠) can be waveguided by selecting the proper slant angle G and period Λ.
Diffraction angle Θ1 must follow grating equation, where nin and nout are refractive

FAQs

What is the smallest grating period you can make?

We are currently able to fabricate down to 300nm. We are working to reduce this further.
Yes. We have successfully combined our in-coupling BPGs and a surface relief out-coupling grating.
We can achieve up to ±40° in the direction of diffraction. The diagonal FOV is significantly larger.

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