Femtosecond laser direct nanolithography of perovskite hydration for temporally programmable holograms.

Modern nanofabrication technologies have propelled significant advancement of high-resolution and optically thin holograms. However, it remains a long-standing challenge to tune the complex hologram patterns at the nanoscale for temporal light field control. Here, we report femtosecond laser direct lithography of perovskites with nanoscale feature size and pixel-level temporal dynamics control for temporally programmable holograms. Specifically, under tightly focused laser irradiation, the organic molecules of layered perovskites (PEA) 2 PbI 4 can be exfoliated with nanometric thickness precision and subwavelength lateral size. This creates inorganic lead halide capping nanostructures that retard perovskite hydration, enabling tunable hydration time constant. Leveraging advanced inverse design methods, temporal holograms in which multiple independent images are multiplexed with low cross talk are demonstrated. Furthermore, cascaded holograms are constructed to form temporally holographic neural networks with programmable optical inference functionality. Our work opens up new opportunities for tunable photonic devices with broad impacts on holography display and storage, high-dimensional optical encryption and artificial intelligence.