Full-visible multifunctional aluminium metasurfaces by in situ anisotropic thermoplasmonic laser printing†
Multifunctional metasurfaces fusing multiple sets of plasmonic antennas within a single layer open a new class of functional optical elements with superior integratability. Even though laser printing of metallic nanostructures has provided a new paradigm for post-customizing metasurfaces in a cost-effective means, the intuitively isotropic thermoplasmonic shape transition adversely tampers with the optical responses of complex plasmonic nanostructures to multiplexed attributes of light, failing advanced multi-functionalities. Herein, we demonstrate full-visible multifunctional metasurfaces by in situ anisotropic laser printing of Al cross nanostructures using single femtosecond pulses. The shape transition and corresponding plasmonic resonances of the two orthogonal arms can be independently and exquisitely modulated in the full-visible range with ultralow cross-talk by controlled irradiations. This is achieved by exploiting polarization-controlled ultrafast thermoplasmonic heating of Al (one-order-of magnitude faster than Ag and Au) and subsequent curvature-driven surface atom migration. Thereby, Janus prints featuring structural color/phase-modulated holographic images can be accomplished with polarization-controlled switches. This newly-developed laser post-printing method can be easily generalized to multiple sets of plasmonic antennas at single pixel levels and thus opens a new strategy to customize complex plasmonic nanostructures for multi-functional flat optics with considerable miniaturization and up-scalability including waveplates, holographic encryption and multiplexed optical storage.