Planar Metasurface Retroreflector
Metasurfaces are two-dimensional arrangements of subwavelength scatterers that control the propagation of optical waves. Here, we show that cascaded metasurfaces, each performing a predefined mathematical transformation, provide a new optical design framework that enables new functionalities not yet demonstrated with single metasurfaces. Specifically, we demonstrate that retroreflection can be achieved with two vertically stacked planar metasurfaces, the first performing a spatial Fourier transform and its inverse, and the second imparting a spatially varying momentum to the Fourier transform of the incident light. Using this concept, we fabricate and test a planar monolithic near-infrared retroreflector composed of two layers of silicon nanoposts, which reflects light along its incident direction with a normal incidence efficiency of 78% and a large half-power field of view of 60°. The metasurface retroreflector demonstrates the potential of cascaded metasurfaces for implementing novel high-performance components, and enables low-power and low-weight passive optical transmitters.
© 2017 Macmillan Publishers Limited, part of Springer Nature. Received 06 October 2016; Accepted 12 May 2017; Published online 19 June 2017. This work was supported by the Jet Propulsion Laboratory, DARPA and Northrop Grumman NG Next. Y.H. acknowledges support from Japan Student Services Organization (JASSO) fellowship. S.M.K. was supported as part of the DOE 'Light–Material Interactions in Energy Conversion' Energy Frontier Research Center under grant no. DE-SC0001293. Device nanofabrication was performed at the Kavli Nanoscience Institute at Caltech. Author Contributions: A.A. and A.F. conceived the concept. A.A. designed and optimized the device. A.A. and E.A. fabricated the sample with help from Y.H. and S.M.K. A.A., E.A. and A.F. designed the experiments. AA. and E.A. performed the measurements and analysed the data. A.A. and A.F. wrote the manuscript with input from all the authors. Competing financial interests: A.A. and A.F. have submitted a patent application based on the idea presented in this work. Data availability: The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.
Supplemental Material - nphoton.2017.96-s1.pdf
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