Abstract
We demonstrate a fast image acquisition technique in the terahertz range via spectral encoding using a metasurface. The metasurface is composed of spatially varying units of mesh filters that exhibit bandpass features. Each mesh filter is arranged such that the centre frequencies of the mesh filters are proportional to their position within the metasurface, similar to a rainbow. For imaging, the object is placed in front of the rainbow metasurface, and the image is reconstructed by measuring the transmitted broadband THz pulses through both the metasurface and the object. The 1D image information regarding the object is linearly mapped into the spectrum of the transmitted wave of the rainbow metasurface. Thus, 2D images can be successfully reconstructed using simple 1D data acquisition processes.
Highlights
(b) finite-difference time-domain (FDTD) simulation results of the transmission of the mesh filters having centre frequencies at 0.2, 0.7, 1.1, 1.6 and 2.0 THz, respectively. (c) Relationship between the sizes and the centre frequencies of the mesh filters
The target is scanned to acquire the image information in the scanning direction while information in the other direction is obtained by the spectrum analysis of the transmitted THz waves
To determine the sizes of the constituent mesh filters, the geometrical parameters of the five mesh filters having centre frequencies, ω c, of 0.2, 0.7, 1.1, 1.6, and 2.0 THz were first obtained by finite-difference time-domain (FDTD) simulation
Summary
To determine the sizes of the constituent mesh filters, the geometrical parameters of the five mesh filters having centre frequencies, ω c, of 0.2, 0.7, 1.1, 1.6, and 2.0 THz were first obtained by finite-difference time-domain (FDTD) simulation. The fabricated rainbow metasurface has a footprint of 20 × 20 mm[2], and the centre frequencies of the mesh filters ranged from 0.2 THz to 2.0 THz. the spectral encoding proportionality The rotation csocnanstnainntgαimwaagsiαng=ex2pπe×2r0i1mm.8mTeHntz. The measured spectral amplitude V(ω, θ) at the rotation angle of θ can be expressed as
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