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Active control of anapole states by structuring the phase-change alloy Ge2Sb2Te5
摘要： High-index dielectric nanoparticles supporting a distinct series of Mie resonances have enabled a new class of optical antennas with unprecedented functionalities. The great wealth of multipolar responses has not only brought in new physical insight but also spurred practical applications. However, how to make such a colorful resonance palette actively tunable is still elusive. Here, we demonstrate that the structured phase-change alloy Ge2Sb2Te5 (GST) can support a diverse set of multipolar Mie resonances with active tunability. By harnessing the dramatic optical contrast of GST, we realize broadband (Δλ/λ ~ 15%) mode shifting between an electric dipole resonance and an anapole state. Active control of higher-order anapoles and multimodal tuning are also investigated, which make the structured GST serve as a multispectral optical switch with high extinction contrasts (>6 dB). With all these findings, our study provides a new direction for realizing active nanophotonic devices.
关键词： active tuning,nanophotonics,phase-change materials,anapole states,GST,Mie resonances
更新于2025-09-19 17:15:36
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[IEEE 2019 Workshop on Recent Advances in Photonics (WRAP) - Guwahati, India (2019.12.13-2019.12.14)] 2019 Workshop on Recent Advances in Photonics (WRAP) - Self-Focusing of Quadruple Gaussian Laser Beam in Relativistic Plasma using Moment Theory Approach
摘要： Phase-change materials and devices have received much attention as a potential route to the realization of various types of unconventional computing paradigms. In this letter, we present non-von Neumann arithmetic processing that exploits the accumulative property of phase-change memory (PCM) cells. Using PCM cells with integrated FET access devices, we perform a detailed study of accumulation-based computation. We also demonstrate efficient factorization using PCM cells, a technique that could pave the way for massively parallelized computations.
关键词： neuromorphic computing,Phase-change materials,non-von Neumann,arithmetic computing
更新于2025-09-19 17:13:59
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Grayscale Nanopatterning of Phase-Change Materials for Subwavelength-Scaled, Inherently Planar, Nonvolatile, and Reconfigurable Optical Devices
摘要： The integration of phase-change materials into the design of optical metasurfaces already enables dynamically switchable, tunable, and reconfigurable optical devices. Their functionality is based on fast and repeatable switching between two stable states - amorphous and crystalline - which is typically accompanied by drastic changes of the electrical and optical properties and can be accomplished by external stimuli. In this study, we demonstrate that focused ion beam irradiation can be used to locally tailor the amount of disorder in phase-change materials in highly confined regions, which was examined both in the visible and mid infrared by using optical nano-imaging techniques such as photo-induced force microscopy and scattering type scanning near-field optical microscopy. Our approach enables grayscale patterning at the nanoscale circumventing the diffraction limit of common laser light sources and thus literally adds a further degree of freedom for the design of optical devices that are subwavelength-scaled, inherently planar, nonvolatile, and reconfigurable.
关键词： focused ion irradiation,grayscale,tailoring disorder,nanopatterning,phase-change materials,nano-imaging
更新于2025-09-19 17:13:59
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Amino-Functionalized Single-Walled Carbon Nanotubes-Integrated Polyurethane Phase Change Composites with Superior Photothermal Conversion Efficiency and Thermal Conductivity
摘要： The development of organic phase change materials (PCMs) with good shape stability, superior photothermal conversion efficiency, and high thermal conductivity is critical for practical photothermal utilizations. Herein, novel form-stable solar-thermal conversion and storage materials (SPCMs) with superior photothermal conversion efficiency and thermal conductivity were successfully synthesized by introducing amino-functionalized single-walled carbon nanotubes (SWNTs?NH2) into poly(ethylene glycol)-based polyurethane PCM. Differential scanning calorimetry (DSC) and thermal conductivity test results showed the SPCMs possessed relatively high phase change enthalpies in the range of 124.0?126.1 J/g and that the introduction of SWNTs?NH2 effectively enhanced the thermal conductivities of SPCMs. Sunlight irradiation experiments showed that the introduction of SWNTs?NH2 into PEG-based polyurethane PCM significantly improved the solar-thermal conversion and storage efficiency of SPCMs from 44.8% to 89.3%. The light irradiation cycling tests and thermogravimetric (TG) analyses indicated that the SPCMs exhibit satisfactory reversible stability and thermal stability. Moreover, SPCMs with SWNTs?NH2 added exhibited much higher solar-thermal conversion and storage efficiency and better reversible stability than SPCM with SWNTs added. In conclusion, the synthesized SPCMs show considerable potential for solar-thermal conversion and storage applications.
关键词： Poly(ethylene glycol),Solar-thermal conversion,Thermal energy storage,Single-walled carbon nanotubes,Phase change materials
更新于2025-09-19 17:13:59
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Structural and electronic properties of liquid, amorphous, and supercooled liquid phases of In <sub/>2</sub> Te <sub/>5</sub> from first-principles
摘要： In2Te5 is a stoichiometric compound in the In–Te system of interest for applications in phase change electronic memories and thermoelectrics. Here, we perform a computational study of the structural, dynamical, and electronic properties of the liquid, supercooled liquid, and amorphous phases of this compound by means of density functional molecular dynamics simulations. Models of the supercooled liquid and amorphous phases have been generated by quenching from the melt. The structure of the liquid phase is characterized by a mixture of defective octahedral and tetrahedral local environments of In atoms, while the amorphous phase displays a mostly tetrahedral local geometry for In atoms with corner and edge sharing tetrahedra similar to those found in the crystalline phases of the In2Te5, InTe, and In2Te3 compounds. Comparison with our previous results on liquid and amorphous In2Te3 and further data on the structural properties of liquid In2Te3 are also discussed. The analysis of the electronic properties highlights the opening of a mobility gap in In2Te5 at about 150 K below the liquidus temperature.
关键词： electronic properties,In2Te5,structural properties,mobility gap,density functional molecular dynamics,phase change materials
更新于2025-09-19 17:13:59
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Surface Polariton‐Like s‐Polarized Waveguide Modes in Switchable Dielectric Thin Films on Polar Crystals
摘要： Surface 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.
关键词： waveguide modes,infrared spectral range,phase-change materials,surface plasmon polaritons,silicon carbide,nanophotonics,Ge3Sb2Te6,surface phonon polaritons,s-polarized light
更新于2025-09-19 17:13:59
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Silicon Photonics at the Interface with a Phase Change Material
摘要： Phase change materials (PCMs) have the ability to control the phase [1], polarization [2], amplitude and coloration [3] of light. Examples of such materials are vanadium dioxide (VO2), GeSbTe and AgInSbTe, which can, owing to changes in their refractive indices, alter the properties of light. Although PCMs have been studied in situations where light propagates from a low-index medium (e.g. air) into the material, there are more possibilities when total internal reflection is involved. In this paper, we investigate the interaction between light travelling in a dense medium with a phase change layer, with particular attention paid to interfaces involving silicon. The possibility of tuning and controlling light at the interface with silicon would be of interest for silicon photonics applications.
关键词： silicon photonics,total internal reflection,vanadium dioxide,Phase change materials,polarization
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Light Manipulation with Plasmonic Structures using Phase Change Materials
摘要： Over the past decade intensive research has focused on the use of plasmonic structures and metamaterials for the control of electromagnetic radiation. Response of such structures is highly dependent on factors set during fabrication, such as the combination of materials used and as well as their structural dimensions. Despite having many promising optoelectronic applications, the inability to tune the optical response of such structures post fabrication presents serious limitations. To overcome this, we present tunable plasmonic elements formed of plasmonic nanostructures on a thin film of vanadium dioxide (VO2), a phase change material. VO2 is an attractive option as a phase change material due to its large, reversible transition from a semiconducting to a metallic phase at a critical temperature of 68°C, close to room temperature. While much research on VO2 is centred on the large changes in the optical properties occurring in the NIR spectral range (above 1μm) upon the phase transition, in this work we focus on the changes in the dielectric function of VO2 in the visible spectral range. In particular, we experimentally and numerically investigate the possibility to use the phase change of VO2 to dynamically tune the plasmonic properties of noble metal nanostructures as well as to manipulate the emission properties of quantum emitters near plasmonic nanostructures. We observe a drastic change in the plasmonic properties of gold nanorods arrays fabricated on a thin layer of VO2 as the phase transition from the semiconducting to metallic phase of VO2 is thermally triggered. Upon phase transition, a >50% decrease in scattering in the red spectral region, especially around 650 nm, was detected in dark field scattering experiments (Figure 1a). Moreover, our spectrally and time resolved measurements reveal that the emission properties of quantum dots (CdSeS/ZnS) in the vicinity of the gold nanorod arrays can be modified through the thermal phase change of the underlying thin layer of VO2 (Figure 1b). When VO2 is in its semiconducting phase the photoluminescence (PL) of QDs on the nanorods array is quenched compared to the PL of QDs on the same VO2 thin film but off the array. In contrast, we observe an enhanced light emission of QDs on the array when the VO2 layer is in its thermally actuated metallic phase. Additionally, the main PL emission peaks of QDs on the nanorod arrays as well as off the arrays red shift by 15 nm, as an effect of heating. The experimental results are accompanied by supporting FDTD simulations.
关键词： photoluminescence,vanadium dioxide,plasmonic structures,quantum dots,phase change materials
更新于2025-09-16 10:30:52
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Research on applications of phase change materials in solar cell thermal control
摘要： In order to grasp the characteristics of phase change material (PCM) in solar cell thermal control, a two-dimensional thermal control structure model of PV/PCM solar cell thermal control system was established, and study was conducted on influence of PCM phase change temperature, thermal conductivity, latent heat value, etc. on the temperature control characteristics of solar cells. The results show that PCM phase change temperature, thermal conductivity, latent heat value will affect solar cell temperature control characteristics in varying degrees. At the same time, thermal control characteristics of PCM are greatly affected by environmental meteorological conditions (solar irradiance, ambient temperature). The research results provide a reference for optimization design of PV/PCM solar cell thermal control system.
关键词： thermal control,phase change materials,solar cell,PV/PCM system
更新于2025-09-16 10:30:52
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8.3: <i>Invited Paper:</i> Ultra High Resolution Display for Digital Holography
摘要： Ultra high resolution display panels are one of the technical trends for future display and essential for the realization of digital hologram. Two approaches for the development toward 1um pixel pitch are introduced. SLM panel with 3μm pixel pitch based on reflected TFT-LCD was fabricated. Reconstructed hologram images were successfully demonstrated. SLM based on phase change materials was under development. In this case the driving circuitry was consist of Si CMOS backplane. Due to the scalability of PCM materials, accomplishment of pixel pitch with 1μm is very promising.
关键词： TFT-LCD,Spatial Light Modulator,Ultra high resolution,Holography,Phase modulation,Active-matrix displays,TFTs,Phase Change Materials
更新于2025-09-12 10:27:22