Shape Retrieval of Azopolymer Surface Relief Gratings from Diffraction Efficiency Measurement

Azopolymers have enormous potential as real-time materials for lithography. Light-induced surface deformations in these polymers enable single-step surface patterning, offering the possibility of fabricating reconfigurable diffractive optical components like gratings. While real-time measurement of the surface geometry is inherently possible, previous methods have relied on complex instruments. Conversely, simple approaches based on real-time diffraction efficiency measurements of a probing light beam have provided only qualitative estimates of the inscription process. Here, we propose a diffraction-based method for the accurate real-time reconstruction of surface relief gratings inscribed on azopolymer films. Our method relies on the acquisition of the diffraction pattern of a probe beam during the SRG formation, and we allowed for surface geometry reconstruction through Fourier decomposition with residual error below 3% and 50 ms temporal resolution. Our all-optical approach, directly integrable in any experimental configuration, provides direct access to the SRG inscription process, enabling real-time feedback for on-demand dynamic surfaces.