Electrically driven reprogrammable phase-change metasurface reaching 80% efficiency

Abstract

Phase-change materials (PCMs) offer a compelling platform for active metaoptics, owing to their large index contrast and fast yet stable phase transition attributes. Despite recent advances in phase-change metasurfaces, a fully integrable solution that combines pronounced tuning measures, i.e., efficiency, dynamic range, speed, and power consumption, is still elusive. Here, we demonstrate an in situ electrically driven tunable metasurface by harnessing the full potential of a PCM alloy, Ge2Sb2Te5 (GST), to realize non-volatile, reversible, multilevel, fast, and remarkable optical modulation in the near-infrared spectral range. Such a reprogrammable platform presents a record eleven-fold change in the reflectance (absolute reflectance contrast reaching 80%), unprecedented quasi-continuous spectral tuning over 250 nm, and switching speed that can potentially reach a few kHz. Our scalable heterostructure architecture capitalizes on the integration of a robust resistive microheater decoupled from an optically smart metasurface enabling good modal overlap with an ultrathin layer of the largest index contrast PCM to sustain high scattering efficiency even after several reversible phase transitions. We further experimentally demonstrate an electrically reconfigurable phase-change gradient metasurface capable of steering an incident light beam into different diffraction orders. This work represents a critical advance towards the development of fully integrable dynamic metasurfaces and their potential for beamforming applications.

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

“…The structure demonstrated here provides the first truly wideband-tunable THG devices and paves the way for the design of nonlinear optical structures with improved efficiency and functionality for a wide range of applications, such as a combined band-and-phase modulation for THG microscopy. These structures can be combined with ultrafast and compact heating processes using indium tin oxide (ITO) Joule heaters, as demonstrated in other studies, [33][34][35] to form a new platform for electrically tunable chip-scale nonlinear optical devices. The structure here can also be a reliable platform for wideband tuning of THG with higher conversion efficiencies: 1) at the longer infrared wavelengths where the GST optical loss is minimal or 2) using alloys of GST, for example, Ge 2 Sb 2 Se 4 Te 1 (in short, GSST), [36,37] which provide less optical loss at the 1100-1600 nm wavelength range.…”

Tunable Infrared Detection, Radiative Cooling and Infrared-Laser Compatible Camouflage Based on a Multifunctional Nanostructure with Phase-Change Material

“…If the temperature continues to rise, the regular crystals inside the cGST slowly turn into disordered nuclei again, and the cGST returns to aGST after undergoing rapid annealing at 640 • C (913.15 K) [57]. The whole reversible phase change process is continuously related to the heating temperature and heating time, and this process and the temperature profile for the reversible phase change operation can be described in various experimental ways [58][59][60][61]. For example, the electrical pulsing schemes and meta-atom temperature profiles are shown by designing an electrothermal metasurface switching [58], and the corresponding temperature responses can be obtained when the GST is heated by a resistive microheater integrated with a phase-change metasurface [59].…”

“…The whole reversible phase change process is continuously related to the heating temperature and heating time, and this process and the temperature profile for the reversible phase change operation can be described in various experimental ways [58][59][60][61]. For example, the electrical pulsing schemes and meta-atom temperature profiles are shown by designing an electrothermal metasurface switching [58], and the corresponding temperature responses can be obtained when the GST is heated by a resistive microheater integrated with a phase-change metasurface [59]. Since GST is non-volatile, once the phase transition is completed, it can maintain the corresponding state at room temperature for a long time, so our research was carried out at room temperature.…”

High resolution multispectral spatial light modulators based on tunable Fabry-Perot nanocavities

“…Active tuning of amplitude, phase or polarization is achieved either by modifying the optical properties of these meta-atoms or those of their surroundings 23 , 24 . Recent studies have demonstrated the use of phase change materials 25 – 31 , transparent conducting oxides 9 , 32 – 34 , two-dimensional materials 35 – 39 , semiconductors 40 – 42 and liquid crystals 10 , 43 – 47 as tuning media, with very few examples achieving individual pixel control 9 , 10 , 34 . Moreover, using the concept of Huygens’ metasurfaces, it is possible to limit the coupling between amplitude and phase modulation 10 , 48 , 49 .…”