Revolutionizing THz Wavefront Control with Metasurfaces
The Power of Metasurfaces
Metasurfaces, composed of subwavelength planar microstructures called meta-atoms, have emerged as a game-changer in the field. These ultrathin metamaterials enable precise control of electromagnetic wavefronts by tailoring their optical responses. By designing metasurfaces with specific phase profiles, scientists have achieved remarkable wave-manipulation effects like anomalous light deflection, polarization manipulation, photonic spin-Hall, and holograms.
Unlocking Dynamic Control
Integrating active elements with individual meta-atoms within passive metasurfaces has led to the development of “active” metadevices capable of dynamically manipulating EM wavefronts. While active elements are easily found in the microwave regime, creating them at higher frequencies like THz has been a challenge due to size restrictions and significant ohmic losses in electronic circuits. This limitation has hindered the dynamic manipulation of THz wavefronts at deep-subwavelength scales.
However, researchers from Shanghai University and Fudan University have recently made a breakthrough. In a study published in Advanced Photonics, they present a novel framework and metadevices for achieving dynamic control of THz wavefronts.
Revolutionary Approach
Instead of locally controlling individual meta-atoms, the researchers employed rotating multilayer cascaded metasurfaces to vary the polarization of a light beam. By rotating different layers, each with a specific phase profile, at different speeds, they were able to dynamically change the effective Jones-matrix property of the entire device. This breakthrough allowed for extraordinary manipulations of the wavefront and polarization characteristics of THz beams.
The researchers demonstrated two metadevices: the first efficiently redirected a normally incident THz beam to scan over a wide solid-angle range, while the second dynamically manipulated both the wavefront and polarization of a THz beam.
A Promising Future
This groundbreaking work offers an attractive and low-cost alternative for dynamic control of THz waves. The researchers envision its potential applications in THz radar, as well as bio- and chemical sensing and imaging.
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