Dielectric metasurfaces possess low intrinsic losses, which are desired in many optical applications. Arrays of dielectric nanostructures have offered the control of light with nanoscale precision, which are typically realized by the state-of-the-art nanofabrication technologies. However, the absorption in metallic or dielectric elements provides a new route for photo-to-thermal conversions and processing. Here we will introduce an optical-field-assisted laser processing (OFLP) technique as a flexible photo-thermal post-writing technology for mass-customization of dielectric metasurfaces.[1]

In OFLP of dielectric metasurfaces, photothermal effects are taking place in the center of the dielectric nanostructures, which helps to gradually control structural and shape modifications of dielectric nanostructures. Depending on the laser pulse energy density, different surface morphologies that support different optical field displays can be created. We applied the optical-field-induced reshaping in color printing. This technology can create laser printed dielectric color metasurfaces with a printing resolution up to 127,000 DPI.[2]

We will further report an in-line optofluidic light trapping device by introducing meta-lenses fabricated by OFLP at the surface of a dielectric silicon metasurface. We post-processed silicon nano-resonators with morphology-dependent optical fields in the visible and in the near infrared. With the excitation of optical fields in the visible, the loss-assisted on-resonance photo-thermal melting of silicon nanostructures ensures that the writing process only takes place at a certain threshold. Under coordinating the double-resonance phase matching condition dynamically, OFLP in the lossy visible band allows the morphology changes of the silicon metasurface with associated spatially modification of the phase and the transmittance in the lossless near infrared band by shifting both resonances.[3]

References:

1. Zhu, X.; Hedayati, M. K.; Raza, S.; Levy, U.; Mortensen, N. A.; Kristensen, A. Digital resonant laser printing: Bridging nanophotonic science and consumer products. Nano Today 2018, 18.

2. Zhu, X.; Yan, W.; Levy, U.; Mortensen, N. A.; Kristensen, A. Resonant-laser-printing of structural colors on high-index dielectric metasurfaces. Sci. Adv. 2017, 3, e1602487.

3. Žukauskas, A.; Zhu, X.; Kristensen, A. Double-resonance-induced resonant laser printing of optical metalens for light trapping. 2019, In preparing.