Bragg Polarization Grating

What is a Bragg Polarization Grating?

A Bragg Polarization Grating (BPG) is a special case of a polarization grating that operates in the Bragg regime or Q>1. It has several unique properties that make it ideal for several applications including augmented and virtual reality.

How It Works

A Bragg polarization grating (BPG) is an optically “thick” grating. BPGs are analogous to Volume Phase Holograms and Volume Bragg Gratings. When operating in the Bragg regime, a polarization grating will diffract only a single polarization (+1st order) and leave the orthogonal polarization un-diffracted. With a circularly polarized input, the efficiency can reach up to 99%. For very wide fields of view, the efficiency can be as high as 90%.

Line drawing of BPG

Technology Comparison

Traditional Grating ImagineOptix BPG
Field of View 20 Degree 60 Degree
Grating Efficiency 40% 99%
Thickness > 100um 2um

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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