Abstract: A method for the generation of volume spatially-resolved holographic data storage within a photosensitive glass sample that incurs changes of optical properties in response to two-photon absorption, the method including directing non-ultraviolet pulsed laser radiation at the photosensitive glass sample to induce changes of optical properties in the glass sample, splitting of the pulsed laser radiation, prior to reaching the glass sample, into an object beam having a direct optical path of a first predetermined length and a reference beam, changing the path of the reference beam to have an indirect optical path of a second pre-determined length, focusing each of the object beam and the reference beam along the respective optical paths, to intersect at a focal volume of the glass sample, and therein to cause the two-photon absorption, providing a variable time delay in the direct path of the object beam so that it reaches the chosen region within the focal volume of glass at the same time as the reference beam,