Dielectric gradient metasurface optical elements

Abstract

Gradient metasurfaces are two-dimensional optical elements capable of manipulating light by imparting local, space-variant phase changes on an incident electromagnetic wave. These surfaces have thus far been constructed from nanometallic optical antennas, and high diffraction efficiencies have been limited to operation in reflection mode. We describe the experimental realization and operation of dielectric gradient metasurface optical elements capable of also achieving high efficiencies in transmission mode in the visible spectrum. Ultrathin gratings, lenses, and axicons have been realized by patterning a 100-nanometer-thick Si layer into a dense arrangement of Si nanobeam antennas. The use of semiconductors can broaden the general applicability of gradient metasurfaces, as they offer facile integration with electronics and can be realized by mature semiconductor fabrication technologies.

Convolution Operations on Coding Metasurface to Reach Flexible and Continuous Controls of Terahertz Beams

“…As 2D artificially engineered structures,1, 2, 3 metasurfaces have attracted great attention in physics and engineering communities owing to a number of unique properties 4, 5, 6, 7, 8, 9, 10, 11, 12. A metasurface is formed by distributing subwavelength resonant particles with different geometries and materials on a 2D surface, and therefore is able to manipulate both amplitudes and phases of electromagnetic (EM) waves, enabling many extraordinary functionalities such as the polarization conversion,,13, 14, 15, 16, 17 perfect absorption,18, 19, 20 and amplitude and phase modulations 21, 22.…”

Self-assembled antireflection coatings for light trapping based on SiGe random metasurfaces

“…Efficient anti-reflection coatings (AR) have been intensively studied with many different approaches having been explored for this purpose [1][2][3] , such as multi-layered thinfilms 4,5 , graded index matching via surface texturing with micro-and nano-structures [6][7][8][9][10][11] , plasmonic metasurfaces [12][13][14] and more recently, metasurfaces [15][16][17][18][19][20][21] based on ordered arrays of sub-micrometric dielectric antennas (dielectric Mie resonators [22][23][24][25][26][27][28] ). Depending on the application of the AR different aspects (lowest value of the total reflectance, broad spectral range, broad acceptance angle, transparency or light trapping) determine the optimal features and fabrication method.…”

Generating stable tractor beams with dielectric metasurfaces

“…Metasurfaces are ideal candidates for generating arbitrary beams since they are compact and have demonstrated extreme control of a wavefront's amplitude, phase, and polarization [27][28][29][30][31][32][33][34]. Dielectric metasurfaces are particularly attractive since they are low loss and can handle high power [35][36][37][38]. The designed metasurface consists of a Si bullseye pattern on a bulk SiO 2 substrate.…”