Multiwavelength metasurfaces through spatial multiplexing

Abstract

Metasurfaces are two-dimensional arrangements of optical scatterers rationally arranged to control optical wavefronts. Despite the significant advances made in wavefront engineering through metasurfaces, most of these devices are designed for and operate at a single wavelength. Here we show that spatial multiplexing schemes can be applied to increase the number of operation wavelengths. We use a high contrast dielectric transmittarray platform with amorphous silicon nano-posts to demonstrate polarization insensitive metasurface lenses with a numerical aperture of 0.46, that focus light at 915 and 1550 nm to the same focal distance. We investigate two different methods, one based on large scale segmentation and one on meta-atom interleaving, and compare their performances. An important feature of this method is its simple generalization to adding more wavelengths or new functionalities to a device. Therefore, it provides a relatively straightforward method for achieving multi-functional and multiwavelength metasurface devices.

MEMS-tunable dielectric metasurface lens

“…Using the criterion given in 50 that is based on the focal spot area increasing to twice its value at the center wavelength, and assuming an effective focal length of~600 μm (corresponding to a numerical aperture of 0.24), the operation bandwidth is given by Δλ = 2.27λ 2 /(fNA 2 ) ≈ 50 nm. To make multiwavelength tunable doublets, many of the recently demonstrated approaches for making multiwavelength metasurfaces can be directly applied 56,[64][65][66] . In addition, the recently introduced concept of phase-dispersion control [67][68][69] can be used to increase the operation bandwidth of the metasurface lenses by correcting the chromatic aberrations over a continuous bandwidth.…”

Coherent control of high efficiency metasurface beam deflectors with a back partial reflector

“…14 However, in the case of beam deflectors, the beam deflection efficiency was somewhat low for the initial proposed design; only a small part of the input light (∼10%) can couple to the MS if there is only a single layer with a conventional MS structure on a dielectric substrate. 1,16 To overcome this, high efficiency MSs have recently been proposed including MSs with an optically-thick back reflector (BR), 2,3 multiple-layered MSs, 17 high aspect ratio all-dielectric MSs, 4,8,12,13 Huygens' MSs, 18 and their combinations. 19 Of these approaches, introducing a BR is the simplest way to obtain the highest beam deflection efficiency (80%-90%) in the broadband regime.…”

“…This relationship can be modified by introducing patterned dielectric/metal nanofilms at the boundary. 1 By properly designing these patterns as in a passive phased array antenna (namely, "metasurfaces (MSs)"), the nanofilms can be used to tailor the wavefront of the input light and obtain myriad functions such as beam-deflection/splitting depending on the polarization, 1-3 polarization conversion and generation, [4][5][6] holograms, 4,7,8 achromatic focusing lenses, [9][10][11][12] optical angular momentum beam conversion, 1,13 and pulse shaping. 14 However, in the case of beam deflectors, the beam deflection efficiency was somewhat low for the initial proposed design; only a small part of the input light (∼10%) can couple to the MS if there is only a single layer with a conventional MS structure on a dielectric substrate.…”

Design of mechanically robust metasurface lenses for RGB colors

“…Multi-wavelength functional metasurface lenses have been explored by different groups 9,34,[38][39][40][41][42][43][44][45][46] . They utilized either polarizations of two-wavelength light 40,43 , or optimization algorithm to broaden the working wavelength range 9,39 .…”

“…They utilized either polarizations of two-wavelength light 40,43 , or optimization algorithm to broaden the working wavelength range 9,39 . For the former case, the two wavelengths are usually purposely selected to have large difference so that their unit structures can have very low electromagnetic interference 38,44 .…”