Ultrathin and flat optical lenses are essential for modern optical imaging, spectroscopy, and energy harvesting. Dielectric metasurfaces comprising nanoscale quasi-periodic resonator arrays are promising for such applications, as they can tailor the phase, amplitude, and polarization of light at subwavelength resolution, enabling multifunctional optical elements. To achieve 2π phase coverage, however, most dielectric metalenses need a thickness comparable to the wavelength, requiring the fabrication of high-aspect-ratio scattering elements. We report ultrathin dielectric metalenses made of van der Waals (vdW) materials, leveraging their high refractive indices and the incomplete phase design approach to achieve device thicknesses down to ∼λ/10, operating at infrared and visible wavelengths. These materials have generated strong interest in recent years due to their advantageous optoelectronic properties. Using vdW metalenses, we demonstrate near-diffraction-limited focusing and imaging and exploit their layered nature to transfer the fabricated metalenses onto flexible substrates to show strain-induced tunable focusing. Our work enables further downscaling of optical elements and opportunities for the integration of metasurface optics in ultraminiature optoelectronic systems.

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范德华超薄金属片

超薄和扁平光学透镜对于现代光学成像，光谱学和能量收集至关重要。包含纳米级准周期谐振器阵列的介电超表面对于此类应用是有前途的，因为它们可以在亚波长分辨率下调整光的相位，幅度和偏振，从而实现多功能光学元件。然而，为了实现2π相覆盖，大多数介电金属感膜需要与波长可比的厚度，从而需要制造高纵横比的散射元件。我们报道了由范德华（vdW）材料制成的超薄介电金属质感，利用它们的高折射率和不完整的相设计方法，可实现在红外和可见光波长下工作的器件厚度低至λλ/ 10。这些材料由于其有利的光电性能，近年来引起了极大的兴趣。使用vdW metalenses，我们演示了近衍射限制的聚焦和成像，并利用它们的分层性质将制造的metalenses转移到柔性基板上，以显示应变诱导的可调聚焦。我们的工作使光学元件的尺寸进一步缩小，并为超微型光电系统中的超表面光学集成提供了机会。