Ultra-thin, high-efficiency metalens in mid-IR
Ultra-thin, high-efficiency metalens in mid-IR
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The mid-infrared (mid-IR) is a strategically important band for numerous applications ranging from night vision to biochemical sensing. Unlike visible or near-infrared optical parts which are commonplace and economically available off-the-shelf, mid-IR optics often require exotic materials or complicated processing, which accounts for their high cost and inferior quality compared to their visible or near-infrared counterparts. Here we theoretically analyzed and experimentally realized a Huygens metasurface platform capable of fulfilling a diverse cross-section of optical functions in the mid-IR. The meta-optical devices feature an ultra-thin profile (1/8 free space wavelength in thickness) and measured optical efficiencies up to 75% in transmissive mode, both of which represent major improvements over state-of-the-art.
Reconfigurable all-dielectric metalens
Reconfigurable all-dielectric metalens
Here we introduce an active metasurface platform combining phase tuning covering the full 2 range and diffraction-limited performance using an all-dielectric, low-loss architecture based on optical phase change materials (O-PCMs). The metalens is constructed using Ge2Sb2Se4Te1 (GSST), an O-PCM with a large refractive index contrast (n > 1) and unique broadband low-loss characteristics in both amorphous and crystalline states. The reconfigurable metalens features focusing efficiencies above 20% at both states for linearly polarized light and a record large switching contrast ratio of 29.5 dB. We further validated aberration-free imaging using the metalens at both optical states, which represents the first experimental demonstration of a non-mechanical active metalens with diffraction-limited performance.
Diffraction-limited fisheye metalens
Diffraction-limited fisheye metalens
Wide field-of-view (FOV) optical functionality is crucial for implementation of advanced imaging and image projection devices. Conventionally, wide FOV operation is attained with a complicated assembly of multiple optical elements known as “fisheye lenses”. Here we present a novel metalens design capable of performing diffraction-limited focusing and imaging over an unprecedented near 180° angular FOV. The lens is monolithically integrated on a one-piece flat substrate and involves only a single layer of metasurface that corrects third-order Seidel aberrations including coma, astigmatism, and field curvature. The metalens further feature a planar focal surface, which enables considerably simplified system architectures for applications in imaging and projection. We fabricated the metalens using Huygens meta-atoms operating at 5.2 μm wavelength and experimentally demonstrated aberration-free focusing and imaging over the entire FOV. The design concept is generic and can be readily adapted to different meta-atom geometries and wavelength ranges to meet diverse application demands.
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