Visible light waveband Dammann grating based on all-dielectric metasurface

Stretchable plasmonic metasurfaces for deformation monitoring

Metasurfaces have recently gained significant attention due to the strong capacity in light field manipulation. However, most traditional metasurfaces are fabricated on rigid substrates, which fix their functionality after fabrication and limit their applications in dynamic measurement fields. In this work, we designed and fabricated a silver metasurface embedded in a stretchable substrate for sensing applications. This metasurface can generate different point cloud patterns under varying stretch ratios when illuminated by a laser beam. By collecting and analyzing the patterns, we can precisely reconstruct the deformation of the metasurface. Furthermore, the sample exhibits excellent performance under incident light of various wavelengths. These results pave the way for developing microdevices with novel capabilities based on flexible metamaterials.

Generating an M2 × N2 spot array with a dual-period hybrid Dammann grating fabricated using maskless projection lithography

The Dammann grating (DG), which redistributes a collimated laser beam into a spot array with a uniform intensity, is a widely adopted approach for profile measurement. Conventional DGs for dense spot projection are binary phase gratings with precisely designed groove structures, which suffer from low efficiency, poor uniformity, and a hard-to-fabricate fine feature size when utilized for a large field of view (FOV). Here, we propose a new, to the best of our knowledge, hybrid DG architecture consisting of two different grating periods which effectively generates an engineering M² × N² spot array with a non-complex structural design. As a proof-of-concept, a dual-period hybrid DG with a two-scale grating period ratio of 11.88 μm/95.04 μm (∼1/8) is designed and fabricated as a means to generate a dense 7²× 7² diffraction spot array with a FOV of 17° × 17°. In addition, the DG exhibits superior performance, with a high efficiency (>60%) and a low non-uniformity (<18%) at a wavelength of 532 nm. This kind of hybrid DG constructed from photoresist patterns with a minimum feature size of ∼1.2 μm can be perfectly fabricated by maskless projection lithography for large-scale and low-cost production. The proposed dual-period hybrid DG can pave the way for depth-perception-related applications such as face unlocking and motion sensing.

Near-unity uniformity and efficiency broadband meta-beam-splitter/combiner

Subwavelength planar structured interfaces, also known as metasurfaces, are ultra-thin optical elements modulating the amplitude, phase, and polarization of incident light using nanostructures called meta-atoms. The optical properties of such metasurfaces can be controlled across wavelengths by selecting geometries and materials of the meta-atoms. Given recent technological developments in optical device miniaturization, components for beam splitting and beam combining are sought for use within these devices as two quintessential components of every optical setup. However, realizing such devices using metasurfaces typically leads to poor uniformity of diffraction orders and narrow-band operation. Using a modified version of particle swarm optimization, we propose and numerically demonstrate a broadband, reciprocal metasurface beam combiner/splitter with uniformity > 97% and diffraction efficiency > 90% in the continuous band from λ=1525 nm to λ=1575 nm. The proposed approach significantly extends the current state of the art of metasurfaces design in terms of uniformity, bandwidth, and efficiency, and opens the door for devices requiring high power or near-unit uniformity.