Abstract
We show that phase-change materials can be used to switch photonic nanostructures between cloaking and superscattering regimes at mid-infrared wavelengths. More specifically, we investigate the scattering properties of subwavelength three-layer cylindrical structures in which the material in the outer shell is the phase-change material Ge2Sb2Te5 (GST). We first show that, when GST is switched between its amorphous and crystalline phases, properly designed electrically small structures can switch between resonant scattering and cloaking invisibility regimes. The contrast ratio between the scattering cross sections of the cloaking invisibility and resonant scattering regimes reaches almost unity. We then also show that larger, moderately small cylindrical structures can be designed to switch between superscattering and cloaking invisibility regimes, when GST is switched between its crystalline and amorphous phases. The contrast ratio between the scattering cross sections of cloaking invisibility and superscattering regimes can be as high as ∼ 93%. Our results could be potentially important for developing a new generation of compact reconfigurable optical devices.
Highlights
In recent years, investigating the interaction of light with subwavelength structures has attracted a lot of attention, since it could potentially lead to a new generation of photonic devices [1,2,3,4,5,6]
We demonstrate that, when GST is switched between its crystalline and amorphous phases, the structure switches between superscattering and cloaking invisibility regimes
For an electrically small three-layer structure, we optimized the dielectric permittivity of the material in the inner shell and the layer dimensions, to switch between cloaking and resonant scattering by switching the phase-change material GST from its crystalline to its amorphous phase
Summary
In recent years, investigating the interaction of light with subwavelength structures has attracted a lot of attention, since it could potentially lead to a new generation of photonic devices [1,2,3,4,5,6]. The optical properties of amorphous GST (aGST) and crystalline GST (cGST) are significantly different These two phases can be switched reversibly and rapidly by applying external electrical pulses, laser pulses or thermal annealing. We show that, when GST is switched between its amorphous and crystalline phases, the structure switches between resonant scattering and cloaking invisibility regimes. We consider the case of a larger, moderately small cylindrical structure In this scenario, we demonstrate that, when GST is switched between its crystalline and amorphous phases, the structure switches between superscattering and cloaking invisibility regimes. Using this theory, we analyze the switching between the cloaking invisibility and enhanced scattering regimes achieved for electrically small and larger, moderately small cylinders in Subsections 3.1 and 3.2, respectively.
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