Abstract
AbstractSurface phonon polaritons (SPhPs) and surface plasmon polaritons (SPPs), evanescent modes supported by media with negative permittivity, are a fundamental building block of nanophotonics. These modes are unmatched in terms of field enhancement and spatial confinement, and dynamical all‐optical control can be achieved, e.g., by employing phase‐change materials. However, the excitation of surface polaritons in planar structures is intrinsically limited to p‐polarization. On the contrary, waveguide modes in high‐permittivity films can couple to both p‐ and s‐polarized light, and in thin films, their confinement can become comparable to surface polaritons. Here, it is demonstrated that the s‐polarized waveguide mode in a thin Ge3Sb2Te6 (GST) film features a similar dispersion, confinement, and electric field enhancement as the SPhP mode of the silicon carbide (SiC) substrate, while even expanding the allowed frequency range. Moreover, it is experimentally shown that switching the GST film grants nonvolatile control over the SPhP and the waveguide mode dispersions. An analytical model is provided for the description of the GST/SiC waveguide mode and it is shown that the concept is applicable to the broad variety of polar crystals throughout the infrared spectral range. As such, complementarily to the polarization‐limited surface polaritons, the s‐polarized waveguide mode constitutes a promising additional building block for nanophotonic applications.
Highlights
SPPs due to the low losses of the driving phonon resonances.[2]
Additional to the restrictions given by total internal reflection that are reflected in the phase differences Φ (Figure 4a), waveguide modes in asymmetric slab waveguides require a minimal film thickness dmin in order to be supported
Our experimental data of the exemplary Ge3Sb2Te6 compound (GST)/SiC system demonstrate that high-contrast active tuning of both modes can be realized via switching of the GST phase, achieving an exceptional tuning figure of merit of up to 7.7
Summary
SPPs due to the low losses of the driving phonon resonances.[2]. Fundamentally, both modes consist of collective charge. Taubner Institute of Physics (IA) RWTH Aachen University 52056 Aachen, Germany sically carry out-of-plane electric fields, and can only be excited by p-polarized light, while no s-polarized light can couple to them This polarization restriction limits the versatility of polariton-based nanophotonics and potentially hinders the development of future technologies, such as emission control[13,14,15] or exploiting solar energy.[16,17] Very recently, omnipolarization waveguide modes in high-permittivity planar media were proposed to. While systems utilizing PCMs have enabled active control over surface polaritons, the large potential of s-polarized waveguide modes in these systems remains, so far, unexploited
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