Printing special surface components for THz 2D and 3D imaging

Abstract

The paper reports an off-axis large focal depth THz imaging system which consists of three 3D printed special surface components (two aspherical mirrors and an axicon). Firstly, the optical design software is used to design and optimize the aspherical parabolic mirror. Secondly, the optimized mirror is prepared by a 3D printing and metal cladding method. Thirdly, a THz axicon is designed for generation of quasi-Bessel Beam and a new geometric theoretical model of oblique incident light for axicon is established. Finally, the imaging system based on the special surface components is constructed. Its maximum diffraction-free distance is about 60 mm, which is 6 times higher than the traditional system. To verify the effectiveness, THz two-dimensional imaging experiments and three-dimensional computed tomography experiment are carried out. The results are consistent with the design and calculations.

Tunable Device for Long Focusing in the Sub-THz Frequency Range Based on Fresnel Mirrors

“…Moreover, while in the former case, the transmission depends on the ohmic losses, which in turn depend on the frequency, in our case, this dependence is significantly reduced, since the reflection of the mirrors is essentially constant over the whole THz range. The problem of long THz focusing has also been solved by assembling conventional systems with rotational symmetry [ 20 ]. In that work, a DOF of 60 mm is reported with a corresponding focal width of 2.8 mm at 0.1 THz with similar problems in terms of focusing performance and lack of tunability compared to our solution.…”

Perfect absorber with separated ‘dielectric–metal–ground’ metamaterial structure

“…The millimeter wave, with frequencies ranging from 30 to 300 GHz and wavelengths ranging from 1 to 10 mm, has earned great attention owing to its distinctive property of 'seeing' through clothing, fog, clouds, smoke and other obstacles, making it attractive for security [1][2][3], medicine [4][5][6], biology [7][8][9][10], and military applications [11][12][13]. Conventional millimeter-wave array imaging has been demonstrated using millimeter-wave receiver arrays based on electrical mechanisms.…”