Multistate Tuning of Third Harmonic Generation in Fano‐Resonant Hybrid Dielectric Metasurfaces

Abstract

Hybrid dielectric metasurfaces have emerged as a promising approach to enhancing near field confinement and thus high optical nonlinearity by utilizing low loss dielectric rather than relatively high loss metallic resonators. A wider range of applications can be realized if more design dimensions can be provided from material and fabrication perspectives to allow dynamic control of light. Here, tunable third harmonic generation (THG) via hybrid metasurfaces with phase change material Ge 2 Sb 2 Te 5 (GST) deposited on top of amorphous silicon metasurfaces is demonstrated. Fano resonance is excited to confine the incident light inside the hybrid metasurfaces, and an experimental quality factor (Q-factor ≈ 125) is achieved at the fundamental pump wavelength around 1210 nm. Not only the switching between a turn-on state of Fano resonance in the amorphous state of GST and a turn-off state in its crystalline state are demonstrated, but also gradual multistate tuning of THG emission at its intermediate states. A high THG conversion efficiency of η = 2.9 × 10 −6 % is achieved, which is 32 times more than that of a GST-based Fabry-Pèrot cavity under a similar pump laser power. Experimental results show the potential of exploring GST-based hybrid dielectric metasurfaces for tunable nonlinear optical devices.

Recent Advances in Tunable Metasurfaces: Materials, Design, and Applications

“…They can be integrated with metallic or dielectric nanostructures to construct hybrid devices or form meta-atoms independently. Besides the amorphous and crystalline states, it has been experimentally validated that GST exhibits intermediate states due to the coexistence of the cubic phase and the hexagonal phase with different ratios, at which its optical constant can be gradually tuned with proper treatment …”

Reversible Tuning of Mie Resonances in the Visible Spectrum

“…Patterning the dielectric nanoantennas directly out of chalcogenide phase change materials (PCMs) can provide nonvolatile and energy-efficient devices with a tunable optical response. − The nonvolatility of chalcogenide PCMs originates from the optical constants being highly sensitive to different atomic bonding configurations. − Among all the PCMs, Ge 2 Sb 2 Te 5 (GST) ,, and its variants are most commonly used in programmable photonics because of the success of Ge 2 Sb 2 Te 5 in phase change optical memory and data storage . However, these data storage PCMs possess small bandgaps of ∼0.5 eV and consequently absorb visible light, reducing the quality-factor of the resonances.…”

Broadband‐Tunable Third‐Harmonic Generation Using Phase‐Change Chalcogenides

“…[ 23 ] There is reported research utilizing the increased loss at the c‐GST phase to exhibit THG off‐state hybridizing with a Fano‐resonant amorphous silicon (a‐Si) metasurface, while the THG response at the less lossy a‐GST phase represents the on‐state. [ 24 ] Note that the tunable third‐order nonlinear optical susceptibility (χ (3) ) of GST at NIR wavelengths [ 25 ] is comparable with that of the widely used a‐Si (≈2.79 × 10 −18 m 2 V −2 ). [ 26 ] Thus, nanoscale devices with GST as the χ (3) media can potentially enable reconfigurable nonlinear devices with reasonably high THG conversion efficiencies and increased nonlinearity.…”