An Etching‐Free Approach Toward Large‐Scale Light‐Emitting Metasurfaces

Abstract

These metasurfaces shape the wavefront by controlling its propagation with local subwavelength phase discontinuities. [4] From the earliest experiments, associated to the reflection of light on arrays of subwavelength metallic patches, [5][6][7] the concept of metasurfaces has rapidly evolved. It started from metallic metasurfaces working at a single wavelength to get to subwavelength high contrast gratings [8][9][10][11] and even subwavelength antenna arrays of various shapes and materials working over a large bandwidth. [12][13][14][15][16][17][18] Today, a broad operation wavelength range is accessible, going from THz down to the visible. Thanks to their reduced thicknesses and high transmission in the visible, the latest metasurface components could enable the next generation of flat optical devices. Large variety of examples of flat and small area components related to dielectric metasurfaces can be found in literature, showing impressive performances and unexpected effects, such as high transmission lenses with high numerical aperture (NA), polarization controlled properties and multiplexed optical information. [19][20][21][22][23][24][25][26][27][28][29] Until recently, metasurfaces have exclusively been considered as passive devices, i.e., their optical properties such as phase, amplitude and polarization responses were considered as fixed with respect to any change of environmental parameters. Their functionalities can be further expanded to a larger extent by designing tunable metasurfaces. Several attempts to achieve this tunability and switching have already been proposed, see for example the modification of the reflectivity and transmission through metasurfaces fabricated from or on the top of phase change materials such as vanadium dioxide, [30][31][32][33] chalcogenides based on germanium antimony telluride [34][35][36] and liquid crystals. [37][38][39] Going beyond the proof of principle of new functionalities and practically implementing these pioneering passive and active devices necessitates new materials, enabling reduced fabrication cost, increased productivity and even higher optical performances. On the other hand, nanofabrication of metasurfaces usually involves several processing steps such as dry etching that induce unavoidable defects degrading the device optical properties and performance.Gallium nitride, an already widespread semiconductor, is selected for the realization of our components, as it offers A new class of quasi 2D optical components, known as metasurfaces and exhibiting exceptional optical properties have emerged in recent years. The scattering properties of their subwavelength patterns allow molding the wavefront of light in almost any desired manner. While the proof of principle is demonstrated by various approaches, only a handful of low cost and fabrication friendly materials are suitable for practical implementations. To further develop this technology toward broadband application and industrial production, new materials and new fabrication methods are required. In a...

Ptychography retrieval of fully polarized holograms from geometric-phase metasurfaces

“…More than 91% conversion efficiency and 2π PB phase coverage can be realized in this configuration. Consequently, the metasurfaces with a footprint of 240 μm × 240 μm are fabricated using conventional nanofabrication process 26 as shown in Fig. 2b.…”

Non-Empirical Large-Scale Search for Optical Metasurfaces

“…The constituent material was set to have a refractive index of 2.3. The dimensions in the unit cells were often reported in actually fabricated metasurfaces [3,5,9,47]. Figure 3a shows a simple metasurface of a square lattice of nano-rods, which has dimensions of 420 × 420 × 680 nm 3 and whose height is 680 nm.…”

“…The constituent material was set to have a refractive index of 2.3. The dimensions in the unit cells were often reported in actually fabricated metasurfaces [ 3 , 5 , 9 , 47 ].…”

“…Designs for metasurfaces have been mostly human knowledge based and optimizations from building blocks known previously. For example, metalenses [ 1 , 2 , 3 , 4 , 5 , 6 ], holograms [ 7 , 8 , 9 ], light absorbers [ 10 , 11 , 12 , 13 , 14 , 15 , 16 ], metagratings [ 17 , 18 , 19 ], luminescence-enhancing metasurfaces [ 20 , 21 , 22 , 23 , 24 , 25 , 26 ], and so on, were fabricated in such ways. The designs for metasurfaces with a particular function are generally elaborate and limited to the domain conceivable from human knowledge, though they are sometimes assisted by optimization algorithms.…”

Large-area pixelated metasurface beam deflector on a 12-inch glass wafer for random point generation

“…For large-area nanostructure patterning, both nanoimprint lithography and photolithography have been developed. Nanoimprint lithography, based on mold, is able to pattern the metasurface by creating a mechanical deformation on an imprint resist [11] or a metasurface layer [12] or by transferring the pattern onto the substrate as etching hard mask [13]. Although these demonstrate the feasibility of nanoimprint lithography for mass production, because of the contact mode of nanoimprinting, there still are concerns about defects, throughput and template wear.…”