Doublet achromatic metalens for broadband optical retroreflector [Early Posting]
Retroreflector that reflects light along its incident direction has found numerous applications in photonics, but the available metasurface schemes suffer from the issue of narrow bandwidth and/or a single angle of incidence. Here a retroreflector using double layers of achromatic gradient metasurfaces is reported, which can realize retroreflection over a continuous range of incidence angles within a wide spectral band. The first metasurface serves as a transmissive achromatic lens that performs a broadband spatial Fourier transform and its inverse, while the second metasurface works as a reflective achromatic lens that undergoes a wavelength- and position-dependent phase dispersions. Using this design strategy, a near-infrared retroreflector comprised of silicon nanopillars with the cross-sections of square pillars and square holes is numerically demonstrated, providing a high-performance retroreflection for polarization-independent incident light waves over a continuous range of incidence angles from 0 to 16° within an extremely broad wavelength range between 1.35 and 1.95 μm. The scheme herein can offer a design strategy of broadband retroreflectors, and impact numerous photonics applications.
作者单位：Huazhong University of Science and Technology
Deng Ming,Ren Tangxuan,Wang Jian,Chen Lin. Doublet achromatic metalens for broadband optical retroreflector[J].Chinese Optics Letters,2021,19(2):02.