Direct Printing of Helical Metal Arrays by Circularly Polarized Light

Abstract

Chiral metasurface with orthogonal nanohelical metal arrays provide strong optical rotation but demands multi-step nanofabrication at low-pressure and/or high-temperature conditions, which is incompatible with many substrates and high-throughput assessment. Submillimeter local photonic patterns with various optical polarization were also hitherto unattainable over the same substrate. Here, we demonstrate direct substrate-tolerant printing of silver nanohelicoids with a locally variable optical activity using circularly polarized light (CPL), producing centimeter-scale chiral metasurface within minutes. The light-illuminated sites on the substrate immersed in an aqueous silver ion solution are activated for heterogeneous nucleation at room temperature. Subsequent CPL-induced asymmetric site-selective deposition and self-assembly of the silver nanoparticles (NPs) sculpt the orthogonal silver helicoids at the interface as one-pot synthesis. The ellipticity and wavelength of the incident photons control the handedness and size of the printed silver helicoids, realizing on-the-fly modulation of optical polarization while printing local patterns. Processing simplicity, high polarization rotation, and fine spatial resolution of the light-driven printing can provide a pathway to the sustainable production of chiral plasmonic metasurfaces, accelerating the development of chiral photonics for health and information technologies.

Unrestricted Chiral Patterning by Laser Writing in Liquid Crystalline and Plasmonic Nanocomposite Thin Films

“…However, as obtained materials are either homochiral, depending on chirality transfer and amplification from constitutionally chiral constituents, or heterochiral, if illuminated with circularly polarized light (CPL) of opposite handedness, incurring the costs of using masks or chiral light sources in the optical processing systems. [48] An interesting example of imprinting both handednesses was recently described by Kotov et al, [49] in which CPL is used to induce the growth of silver nanoparticle assemblies showing a helical geometry. By controlling the handedness of CPL light and by using a motorized stage, patterns showing bi-polar chiroptical response were achieved.…”