Patent ID: 7326500

Claim:
A method of efficiently generating holograms from photo-thermo-refractive (PTR) glasses having a diffraction efficiency of at least approximately 90%, comprising the steps of: providing a PTR glass blank having a total contamination with iron and heavy metals of a few ppm; exposing the PTR glass blank with a UV light source or other source of ionizing radiation to create precursors of nucleation centers which are color centers; generating a visible light having an intensity greater than approximately 10 MW/cm 2 ; exposing the UV exposed PTR glass blank containing precursors of nucleation centers with the high intensity visible light greater than approximately 10 MW/cm 2 to decrease concentration of the precursors to decrease the rate of crystallization at the development stage to increase a refractive index in the PTR glass after exposure to the visible light to record the hologram, wherein the visible light exposure of the UV exposed PTR glass blank causes a nonlinear transformation of nucleation centers; thermal treating the PTR glass exposed to both the UV and visible radiation to provide phase transformation depending on an amount and intensity of a visible radiation to allow crystal growth in the UV exposed area using a nonlinear mechanism for destruction of nucleation centers in the area exposed to visible light; cooling the thermal treated PTR glass to room temperature to provide refractive index variations according to the amount and intensity of the visible radiation, wherein a difference between refractive indices in the UV exposed areas and the UV and visible light exposed areas allows hologram recording by visible light radiation; and replaying the hologram from the exposed and thermal treated PTR glass by long wavelength radiation.