Effect of Zeroth-Order beam on Azobenzene Polymer Surface Relief Gratings Fabricated by Phase-Mask Method

In the fabrication of surface relief gratings (SRGs) on azobenzene polymer films with a zeroth-order suppressed diffraction phase mask, it is found that the SRGs' relief figure and period change with the irradiation time, and the period is doubled after a critical time. The time dependence of the changes in the SRG forming process is investigated by theoretical analysis and experiments. An optimum time range for inscription of the sub-micron SRGs is determined to be 5-8 min in terms of both the theoretical and experimental results.