Large regular arrays with submicron domains written by low-voltage e-beam on –Z cut of lithium niobate

Abstract

Contact-free formation of large arrays with a uniform distribution of submicron size domains on the LiNbO3 surface is an urgent and not fully solved problem. Such arrays are widely used, including in optical quasi-phase matching devices for nonlinear frequency conversion. In this work large arrays of submicron domains were first written using low-voltage electron-beam irradiation on a –Z cut of a bulk lithium niobate sample with a grounded conductive coating. Very uniform periodic structures of submicron domains with periods of 1 μm or 1.5 μm were obtained at 5 kV and 10 kV. Surface etching was used to identify the domains within days of electron beam writing. It was found that the stability of the submicron domains became worse as the area of the irradiated squares used in the writing schemes decreased. The spatial intervals between the squares also affect the regularity of the arrays formed. When interpreting the experimental data obtained, the results of electric field distribution simulation at the corresponding writing schemes were used. Based on these results, it has been suggested that two effects competitively influence the success of large regular arrays of submicron domains formation. The electrostatic repulsion between the closest submicron domains and the convergence of electron-beam charges up to the formation of sufficiently large merging zones in which the electric field has sufficient strength. The conclusions obtained could be useful for understanding the mechanism of submicron domain formation in the injected charge zones and could contribute to the further development of electron-beam domain engineering.