Department of Physics , University of Washington , Seattle , Washington 98195 , United States.
Institute of Photonics Technologies , National Tsing Hua University , Hsinchu 30013 , Taiwan.
Nano Lett. 2018 Nov 14;18(11):6961-6966. doi: 10.1021/acs.nanolett.8b02875. Epub 2018 Oct 15.
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.
超薄和扁平的光学透镜对于现代光学成像、光谱学和能量收集至关重要。由纳米级准周期谐振器阵列组成的介电超表面在这些应用中很有前途，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，实现多功能光学元件。然而，为了实现 2π 相覆盖，大多数介电金属镜需要与波长相当的厚度，这需要制造高纵横比的散射元件。我们报告了由范德华（vdW）材料制成的超薄介电金属镜，利用其高折射率和不完全相位设计方法将器件厚度降低到 ∼λ/10，在红外和可见光波长下工作。由于其有利的光电性能，这些材料近年来引起了强烈的兴趣。使用 vdW 金属镜，我们演示了近衍射极限聚焦和成像，并利用其层状结构将所制造的金属镜转移到柔性衬底上，以展示应变诱导的可调聚焦。我们的工作使光学元件进一步小型化，并为超小型光电系统中集成介面光学提供了机会。
