Dielectric optical nanoantennas are promising as fundamental building blocks in next generation color displays, metasurface holograms, and wavefront shaping optical devices. Due to the high refractive index of the nanoantenna material, they support geometry-dependent Mie resonances in the visible spectrum. Although phase change materials, such as the germanium–antimony–tellurium alloys, and post-transition metal oxides, such as ITO, have been used to tune antennas in the near-infrared spectrum, reversibly tuning the response of dielectric antennas in the visible spectrum remains challenging. In this paper, we designed and experimentally demonstrated dielectric nanodisc arrays exhibiting reversible tunability of Mie resonances in the visible spectrum. We achieved tunability by exploiting phase transitions in Sb2S3 nanodiscs. Mie resonances within the nanodisc give rise to structural colors in the reflection mode. Crystallization and laser-induced amorphization of these Sb2S3 resonators allow the colors to be switched back and forth. These tunable Sb2S3 nanoantenna arrays could enable the next generation of high-resolution color displays, holographic displays, and miniature LiDAR systems.

The unique optical properties of phase change materials (PCMs) can be exploited to develop efficient reconfigurable photonic devices. Here, we design, model, and compare the performance of programmable 1 × 2 optical couplers based on: Ge2Sb2Te5, Ge2Sb2Se4Te1, Sb2Se3, and Sb2S3 PCMs. Once programmed, these devices are passive, which can reduce the overall energy consumed compared to thermo-optic or electro-optic reconfigurable devices. Of all the PCMs studied, our ellipsometry refractive index measurements show that Sb2S3 has the lowest absorption in the telecommunications wavelength band. Moreover, Sb2S3 -based couplers show the best overall performance, with the lowest insertion losses in both the amorphous and crystalline states. We show that by growth crystallization tuning at least four different coupling ratios can be reliably programmed into the Sb2S3 directional couplers. We used this effect to design a 2-bit tuneable Sb2S3 directional coupler with a dynamic range close to 32 dB. The bit-depth of the coupler appears to be limited by the crystallization stochasticity.

The Coopersmith Self-Esteem Inventory (SEI) was examined using a modified version of the Sabers and Whitney model for construct validation. The SEI, Piers-Harris Children's Self-Concept Scale (CSCS), and Children's Social Desirability Scale (CSDS) were administered to 55 males and 50 females enrolled in six intact fifth-grade classes. Each student also received a teacher rating of self-concept using the Coopersmith Behavioral Academic Assessment Scale (BASE). Regression analyses indicated that the SEI has convergent validity with regard to the CSCS ( p < .01) and BASE ( p < .01), has discriminant validity with regard to the CSDS ( p > .05), is sensitive to differences in achievement level ( p < .01), and is internally consistent (coefficient alpha = .86). Intra-rater stability for the BASE ranged from .85 to .97; average inter-rater agreement was .86.

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All‐dielectric metasurfaces provide unique solutions for advanced wavefront manipulation of light with complete control of amplitude and phase at sub‐wavelength scales. One limitation, however, for most of these devices is the lack of any post‐fabrication tunability of their response. To break this limit, a promising approach is employing phase‐change materials (PCMs), which provide fast, low energy, and non‐volatile means to endow metasurfaces with a switching mechanism. In this regard, great advancements have been done in the mid‐infrared and near‐infrared spectrum using different chalcogenides. In the visible spectral range, however, very few devices have demonstrated full phase manipulation, high efficiencies, and reversible optical modulation. In this work, a programmable all‐dielectric Huygens’ metasurface made of antimony sulfide (Sb2S3) PCM is experimentally demonstrated, a low loss and high‐index material in the visible spectral range with a large contrast (≈0.5) between its amorphous and crystalline states. ≈2π phase modulation is shown with high associated transmittance and it is used to create programmable beam‐steering devices. These novel chalcogenide PCM metasurfaces have the potential to emerge as a platform for next‐generation spatial light modulators and to impact application areas such as programmable and adaptive flat optics, light detection and ranging (LiDAR), and many more.