Nonlinear metasurfaces with high conversion efficiencies have been vastly investigated. However, strong dynamic tunability of such devices is limited in conventional passive plasmonic and dielectric material platforms. Germanium antimony telluride (GST) is a promising phase-change chalcogenide for the reconfiguration of metamaterials due to strong nonvolatile changes of the real and imaginary parts of the refraction index through amorphous-crystalline phase change. The orderly structured GST has an even higher potential in tunable second-harmonic generation (SHG) with a non-centrosymmetric crystal structure at the crystalline phase, while the amorphous phase of GST does not exhibit bulk second-order nonlinearity. Here, we experimentally demonstrate SHG switches by actively controlling the crystalline phase of GST for a GST-based hybrid metasurface featuring a gap-surface plasmon resonance, and a quarter-wave asymmetric Fabry–Perot (F–P) cavity incorporating GST. We obtain SHG switches with modulation depths as high as ∼ 20 dB for the wavelengths at the on-state resonance. We also demonstrate the feasibility of multi-level SHG modulation by leveraging three controlled GST phases, i.e., amorphous, semi-crystalline, and crystalline, for the gap-surface plasmon hybrid device, which features stronger light–matter interaction and has higher resonant SHG efficiencies than the asymmetric F–P cavity device at respective GST phases. This research reveals that GST-based dynamic SHG switches can be potentially employed in practical applications, such as microscopy, optical communication, and photonic computing in the nonlinear regime.

中文翻译：

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使用包含相变硫族化物的混合纳米结构动态可调谐二次谐波产生

具有高转换效率的非线性超表面已被广泛研究。然而，此类器件的强动态可调性在传统的无源等离子体和介电材料平台中受到限制。锗锑碲化物 (GST) 是一种很有前途的相变硫族化物，可用于超材料的重构，因为通过非晶晶相变的折射率的实部和虚部发生强烈的非易失性变化。有序结构的 GST 在可调谐二次谐波产生 (SHG) 方面具有更高的潜力，在结晶相具有非中心对称晶体结构，而 GST 的非晶相不表现出体二阶非线性。这里，我们通过主动控制 GST 的结晶相位来实验证明 SHG 开关，用于基于 GST 的混合超表面，具有间隙表面等离子体共振和包含 GST 的四分之一波非对称法布里-珀罗 (F-P) 腔。对于通态谐振的波长，我们获得了调制深度高达 20 dB 的 SHG 开关。我们还通过利用三个受控的 GST 相（即非晶、半晶和晶）证明了多级 SHG 调制的可行性，用于间隙表面等离子体混合器件，该器件具有更强的光物质相互作用和更高的共振 SHG在各个 GST 阶段，效率比非对称 F-P 腔器件高。这项研究表明，基于 GST 的动态 SHG 开关可以潜在地用于实际应用，例如显微镜、