All-dielectric metasurfaces comprising arrays of nanostructured high-refractive-index materials are re-imagining what is achievable in terms of the manipulation of light. However, the functionality of conventional dielectric-based metasurfaces is fixed by design; thus, their optical response is locked in at the fabrication stage. A far wider range of applications could be addressed if dynamic and reconfigurable control were possible. We demonstrate this here via the novel concept of hybrid metasurfaces, in which reconfigurability is achieved by embedding sub-wavelength inclusions of chalcogenide phase-change materials within the body of silicon nanoresonators. By strategic placement of an ultra-thin G e 2 S b 2 T e 5 layer and reversible switching of its phase-state, we show individual, multilevel, and dynamic control of metasurface resonances. We showcase our concept via the design, fabrication, and characterization of metadevices capable of dynamically filtering and modulating light in the near infrared (O and C telecom bands), with modulation depths as high as 70% and multilevel tunability. Finally, we show numerically how the same approach can be re-scaled to shorter wavelengths via appropriate material selection, paving the way to additional applications, such as high-efficiency vivid structural color generators in the visible spectrum. We believe that the concept of hybrid all-dielectric/phase-change metasurfaces presented in this work could pave the way for a wide range of design possibilities in terms of multilevel, reconfigurable, and high-efficiency light manipulation.
Reduction of the wavelength in on-chip light circuitry is critically important not only for the sake of keeping up with Moore's law for photonics but also for reaching toward the spectral ranges of operation of emerging materials, such as atomically thin semiconductors, vacancy-based single-photon emitters, and quantum dots. This requires efficient and tunable light sources as well as compatible waveguide networks. For the first challenge, halide perovskites are prospective materials that enable cost-efficient fabrication of micro-and nanolasers. On the other hand, III−V semiconductor nanowires are optimal for guiding of visible light as they exhibit a high refractive index as well as excellent shape and crystalline quality beneficial for strong light confinement and long-range waveguiding. Here, we develop an integrated platform for visible light that comprises gallium phosphide (GaP) nanowires directly embedded into compact CsPbBr 3 -based light sources. In our devices, perovskite microcrystals support stable room-temperature lasing and broadband chemical tuning of the emission wavelength in the range of 530−680 nm, whereas GaP nanowaveguides support efficient outcoupling of light, its subwavelength (<200 nm) confinement, and long-range guiding over distances more than 20 μm. As a highlight of our approach, we demonstrate sequential transfer and conversion of light using an intermediate perovskite nanoparticle in a chain of GaP nanowaveguides.
Laser-induced periodic surface structures (LIPSS) can be fabricated in virtually all types of solid materials and show great promise for efficient and scalable production of surface patterns with applications in various fields from photonics to engineering. While the majority of LIPSS manifest as modifications of the surface relief, in special cases, laser impact can also lead to periodic modulation of the material phase state. Here, we report on the fabrication of high-quality periodic structures in the films of phase-change material Ge2Sb2Te5 (GST). Due to considerable contrast of the refractive index of GST in its crystalline and amorphous states, the fabricated structures provide strong spatial modulation of the optical properties, which facilitates their applications. By changing the excitation laser wavelength, we observe the scaling of the grating period as well as transition between formation of different types of LIPSS. We optimize the laser exposure routine to achieve large-scale high-quality phase-change gratings with controllable period and demonstrate their reversible tunability through intermediate amorphization steps. Our results reveal the prospects of fast and rewritable fabrication of high-quality periodic structures for photonics and can serve as a guideline for further development of phase-change material-based optical elements.
All-dielectric metasurfaces and nanoantennas offer unprecedented flexibility and efficiency of manipulation of light at the nanoscale. Still, the functionality of conventional dielectric-based devices is fixed-by-design, i.e. the response is locked-in at the fabrication stage. To address the challenges offered by modern nanophotonics, active, dynamic and reconfigurable control of such structures is required. Here, we demonstrate active all-dielectric devices enabled by embedding subwavelength chalcogenide phase-change material inclusions in the volume of main silicon nanoresonators. We validate the concept via the design and development of a metasurface for active spectral filtering in the near infrared and a subwavelength nanoantenna providing complete switching of surface plasmon-polariton directivity pattern.
Using a femtosecond laser radiation, we generated hollow carbon spheres and hemispheres from 1D and 2D MOFs.
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