Reprogrammable surface relief diffraction gratings from azopolymer photopatterning

Flat patterned surfaces, traditionally fabricated using standard lithographic techniques, can manipulate the wavefront of light within wavelength-scale thicknesses, offering enormous potential for scientific and technological innovation. Amorphous polymers containing azobenzene molecules provide a compelling alternative to conventional photoresists, enabling the direct and fully optical fabrication of reconfigurable flat optical devices. In this work, I combine azopolymers with holographic illumination to achieve maskless, reversible fabrication of diffraction gratings with real-time surface monitoring and control. An accurate model describing the diffraction behavior ensures predictable optical performance and guides the design of optimized surface profiles. Furthermore, this method extends beyond simple periodic structures to more complex geometries, including chirped gratings and optical Fourier surfaces, significantly expanding the functional capabilities of programmable flat optics, even through multiple reprogramming cycles.