Imprinting phase/amplitude patterns in glasses with thermal poling

A new technique to imprint phase and amplitude patterns into glass is proposed. The technique is based on the thermal poling of oxide glasses via a figurate plane anode which has a relief with a given 2D modulation of the pattern depth. Poling with such an anode results in the subsurface layer depleted of high-mobility ions and characterized by 2D modulation of its thickness directly determined by the relief of the anode pattern. Due to the 0.02 difference in refractive indices of the depleted layer and bulk glass, glasses poled via the figurate anode operate like optical phase structures, e.g. diffraction phase gratings in the case of a regular pattern. It is found that phase contrast in such structures (for the glasses used in this work) increases linearly with the total charge passing through the glass sample in the process of poling, with the maximal achieved phase contract of 1.32π. If initial glass contains silver ions, the bottom of the depleted layer can be treated as a latent relief image of the anode relief pattern, which can be visualized by heat treatment in H2 atmospheres due to the formation of silver nanoparticles absorbing visible light. Physico-chemical processes involved in the structure formation are discussed.