Mie resonance engineering in meta-shell supraparticles for nanoscale nonlinear optics

TL;DR

This paper introduces meta-shell supraparticles with engineered Mie resonances that significantly enhance second harmonic generation, offering new opportunities for nonlinear nanophotonics in colloidal platforms.

Contribution

The study demonstrates the design and fabrication of dielectric meta-shell supraparticles with tunable Mie resonances that greatly improve nonlinear optical responses.

Findings

Achieved several orders of magnitude enhancement in SHG.

Reported an absolute conversion efficiency of 10^-7.

Showed potential for scalable, tunable nonlinear nanophotonics.

Abstract

Supraparticles are coordinated assemblies of discrete nanoscale building blocks into complex and hierarchical colloidal superstructures. Holistic optical responses in such assemblies are not observed in an individual building block or in their bulk counterparts. Furthermore, subwavelength dimensions of the unit building blocks enable engraving optical metamaterials within the supraparticle, which thus far has been beyond the current pool of colloidal engineering. This can lead to effective optical features in a colloidal platform with unprecedented ability to tune the electromagnetic responses of these particles. Here, we introduce and demonstrate the nanophotonics of meta-shell supraparticle (MSP), an all dielectric colloidal superstructure having an optical nonlinear metamaterial shell conformed onto a spherical core. We show that the metamaterial shell facilitates engineering the Mie resonances in the MSP that enable significant enhancement of the second harmonic generation (SHG). We show several orders of magnitude enhancement of second-harmonic generation in an MSP compared to its building blocks. Furthermore, we show an absolute conversion efficiency as high as 10^-7 far from the damage threshold, setting a new benchmark for SHG with low-index colloids. The MSP provides pragmatic solutions for instantaneous wavelength conversions with colloidal platforms that are suitable for chemical and biological applications. Their engineerability and scalability promise a fertile ground for nonlinear nanophotonics in the colloidal platforms with structural and material diversity.