| CPC G02B 6/02171 (2013.01) [G02B 6/02123 (2013.01)] | 20 Claims |

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1. A three-dimensional Bragg grating, comprising:
a single colloidal crystal that:
includes periodic particles and interstitial material, and
due to having been grown in a micro-gravity environment:
is topological defect free; and
lacks a high-density glass phase.
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