Proprietary technology of high efficiency diffractive optical elements manufactured at OptiGrate is based on a linear photosensitivity in a BragGlass™ (so-called photo-thermo-refractive or PTR glass) which is a silicate glass doped with cerium, silver, and fluorine.

The precipitation of a minor crystalline phase after UV-exposure and thermal development induces a refractive index change to create a holographic phase pattern throughout the whole glass volume.

BragGlass™ properties

  • Photosensitivity ranges from 280 to 350 nm
  • Transparency from 350 to 2700 nm
  • Absorption in the near IR region below 0.0001 cm-1
  • Refractive index 1.49
  • Abbe number 60
  • Photo-induced refractive index increment up to 1200 ppm
  • Spatial frequencies from 0 (zero) to 10,000 mm-1
  • Phase pattern cannot be erased by any type of optical or ionizing radiation

Absorption spectrum of BragGlass™