Uniform Huygens Metasurfaces with Postfabrication Phase Pattern Recording Functionality

With the rapid progress in the field of metasurfaces and their use in miniature integrated devices arises the quest for cheap mass production of efficient metasurfaces. We suggest a novel way to design and fabricate phase-gradient Huygens metasurfaces using laser-annealing of uniform particles made of As₂S₃ chalcogenide glass. We show that a phase gradient metasurface can be realized by tuning the refractive index of otherwise identical meta-atoms instead of tuning their geometry. We are using an array of identical As₂S₃ particles with the possibility to locally change their refractive index using a short-wavelength illumination (green laser) in order to tune the phase pattern at the postfabrication stage. Metasurfaces fabricated with this method can be used for operation in the red or IR spectral range. We fabricate uniform As₂S₃ Huygens metasurfaces using electron beam lithography and demonstrate their postfabrication tuning with exposure of comparatively low intensity. Sample characterizations with transmittance measurements and quantitative phase microscopy provide results in good correspondence with numerical predictions confirming postfabrication spectral tuning. Using such tuning, we demonstrate the possibility of transferring the intensity pattern produced by modifying a writing beam with a spatial light modulator to a phase pattern recorded on a uniform As₂S₃ metasurface. Our method has potential advantages for the low-cost production of large-scale metasurfaces because uniform geometries are better adjusted for mass manufacturing.