Metasurface Optics With On-Axis Polarization Control for Terahertz Sensing Applications
IEEE Transactions on Terahertz Science and Technology(2023)
摘要
Nondestructive testing (NDT) and imaging of materials with unknown properties are important applications of terahertz technology. Different contrast-forming methods are available to obtain diverse information on the imaged region, including intensity, color, phase, and polarization. Polarimetric imaging is relatively under-investigated owing to the difficulty in its implementation with complex optical arrangements. In this article, we present the design and monolithic fabrication of an anisotropic metasurface that incorporates several beam-forming functions in a single layer with high efficiency thus simplifying instrument construction. The probe beam generated by the metasurface consists of an orthogonally polarized pair of collinear Bessel beams that create a well-defined on-axis change of polarization. The metasurface is integrated into a polarimetric imaging microscope for 3-D beam profiling and sensing experiments at 2.52 THz. An analytical model to describe the on-axis polarization variation was found to be in excellent agreement with both finite-difference time-domain (FDTD) simulations and the experimental results. The setup was used to measure the refractive index and diattenuation of homogeneous sample regions in a proof-of-principle application. We anticipate this technology will find future applications in NDT and polarimetric imaging of polymer composites and 3-D profilometry of reflective surfaces.
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关键词
Dielectric materials, metasurfaces, nondestructive testing, optical polarization, terahertz wave imaging
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