Catenary-based phase change metasurfaces for mid-infrared switchable wavefront control

Active wave manipulation by ultracompact meta-devices is highly embraced in recent years, but a major concern still exists due to the lack of functional reconfigurability. Moreover, the phase or amplitude discontinuities introduced by collective response of discrete meta-atoms make current meta-devices far from practical applications. Here, we demonstrate actively tunable wavefront control with high-efficiency by combining catenary-based meta-atoms for intrinsic continuous phase regulation with the chalcogenide phase change material (PCM) of Ge2Sb2Te5. First, switchable beam deflection is demonstrated in a wide mid-IR range between 8 mu m and 9.5 mu m with 'on' and 'off' states for beam steering between anomalous and normal specular reflections. Second, a switchable meta-axicon for zero order Bessel beam generation is demonstrated with full width at half maximum (FWHM) as small as similar to 0.41 lambda (lambda. = 12 mu m). As a result, our scheme for active and continuous phase control potentially paves an avenue to construct active photonic devices especially for applications where large contrast ratio is highly desirable, such as optoelectronic integration, wavefront engineering and so on. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Automated summary

Active wavefront control with high efficiency is demonstrated by combining catenary-based meta-atoms with chalcogenide phase change material (PCM), showing switchable beam deflection and meta-axicon for zero order Bessel beam generation, paving the way for constructing active photonic devices with large contrast ratio.