Thermally Controllable Multiple High Harmonics Generation by Phase-Change Materials-Mediated Fano Clusters

TL;DR

This paper demonstrates how phase-change materials can be used to thermally control and enhance multiple high-order harmonic generation in nanophotonic clusters, enabling tunable nonlinear optical responses.

Contribution

It introduces a novel hetero-metallodielectric nanocluster with phase-change materials that allows dynamic control of high harmonic generation through thermal phase transitions.

Findings

Significant enhancement of second and third harmonic generation efficiencies.

Distinct harmonic wavelengths achieved in amorphous and crystalline phases.

The cluster enables tunable nonlinear optical responses for future photonic devices.

Abstract

Substantial enhancement of nonlinear high-order harmonics generation based on Fano-resonant nanostructures has received growing interest due to their promising potential for developing integrated and advanced next-generation nanophotonic devices. In this study, going beyond conventional subwavelength structures, we propose an optothermally functional hetero-metallodielectric asymmetric eight-member octamer cluster composed of a central silicon nanodisk and peripheral disks with a phase-change material (Ge2Sb2Te5). Using full electromagnetic calculations, we show that in the amorphous phase of the surrounding particles, the oligomer acts as an all-dielectric cluster, while in the crystalline regime, the octamer turns into a hybrid metallodielectric assembly. Exploiting the exquisite ability of supporting distinct Fano lineshapes at different wavelengths depending on the phase of Ge2Sb2Te5, we showed the generation of both second and third harmonics at amorphous and crystalline phases of GST nanodisks, respectively with the produced harmonic wavelengths of 425 nm and 317 nm, respectively. Our calculations for the corresponding conversion efficiencies revealed significant enhancements as {\eta}SHG=0.012% and {\eta}THG=0.0081% for SHG and THG, respectively. Such an exquisite feature of multiresonant optothermally tunable cluster allows generation of several higher-harmonics with distinct intensities using a single system for future photonics applications.