Terahertz imaging in dielectric media with quasi-Bessel beams

Zhang, Zhuopeng; Buma, Takashi

doi:10.1117/12.875864

Cited by 10 publications

(5 citation statements)

References 11 publications

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“…The Bessel beam was first described by Durnin in 1987 [16] and several methods to generate it were subsequently proposed including the axicon. The axicon has already been explored in the THz field in numerous applications including 3d imaging [17] and tomography [18,19].…”

Section: A Backgroundmentioning

confidence: 99%

Submillimeter-Wave Cornea Phantom Sensing Over an Extended Depth of Field With an Axicon-Generated Bessel Beam

Baggio

Tamminen

Lamberg

et al. 2023

IEEE Trans. THz Sci. Technol.

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The feasibility of a 220 -330 GHz zero order axicon generated Bessel beam for corneal water content was explored. Simulation and experimental data from the 25-degree cone angle hyperbolic-axicon lens illuminating metallic spherical targets demonstrate a monotonically decreasing, band integrated, backscatter intensity for increasing radius of curvature from 7 -11 mm, when lens reflector and optical axis are aligned. Further, for radii >= 9.5 mm, maximum signal was obtained with a 1 mm transverse displacement between lens and reflector optical axes arising from spatial correlation between main lobe and out of phase side lobes. Thickness and permittivity parameter estimation experiments were performed on an 8 mm radius of curvature, 1 mm thick fused quartz dome over a 10 mm axial span. Extracted thickness and permittivity varied by less than ~ 25 μm and 0.2 respectively after correction for superluminal velocity. Estimated water permittivity and thickness of water backed gelatin phantoms showed significantly more variation due to a time varying radius of curvature. To the best of our knowledge, this is the first work that describes axicon generated Bessel beam measurements of layered spheres with varying radii of curvature, in the submillimeter range.

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Section: A Backgroundmentioning

confidence: 99%

Submillimeter-Wave Cornea Phantom Sensing Over an Extended Depth of Field With an Axicon-Generated Bessel Beam

Baggio

Tamminen

Lamberg

et al. 2023

IEEE Trans. THz Sci. Technol.

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“…Accordingly, THz large focal depth imaging based on axicons attracts increasing attentions. In 2011, Zhang et al reported THz imaging in dielectric media with quasi-Bessel beams 15 . Since then, THz imaging technology based on axicons has been widely studied [16][17][18][19] .…”

Section: Printing Special Surface Components For Thz 2d and 3d Imaginmentioning

confidence: 99%

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

Yan

Wang

Zhao

et al. 2020

Sci Rep

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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.

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“…Among the different optical functions, long-focusing by means of the generation of quasi-Bessel beams (QBBs) is one of the most studied because of the potential benefits in many fields, like remote sensing, optical trapping, and sensing [20]. Currently, the most common approaches, like Computer Numerical Control (CNC), injection molding, milling [21][22][23], and ultrashort pulsed laser ablation [24], are still time-consuming and costly. Aiming to overcome these drawbacks, recent progresses in 3D printing have been successfully exploited to produce less expensive and even exotic geometries for THz devices [25][26][27][28][29], but at the moment, the resolution of conventional 3D printers (~100 µm) limits the quality of the finishing of the surfaces, and as a consequence, 3D-printed devices usually operate at wavelengths no lower than 500 µm.…”

Section: Introductionmentioning

confidence: 99%

Long-Focusing Device for Broadband THz Applications Based on a Tunable Reflective Biprism

Margheri,

Del Rosso

2023

Micromachines

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THz radiation has assumed great importance thanks to the efforts in the development of technological tools used in this versatile band of the electromagnetic spectrum. Here, we propose a reflective biprism device with wavelength-independent long-focusing performances in the THz band by exploiting the high thermo-mechanical deformation of the elastomer polydimethylsiloxane (PDMS). This deformation allows for achieving significant optical path modulations in the THz band and effective focusing. The surface of a PDMS layer is covered with a gold thin film acting as a heater thanks to its absorption of wavelengths below ~500 nm. An invariance property of the Fresnel integral has been exploited to experimentally verify the THz performances of the device with an ordinary visible laser source, finding excellent agreement with the theoretical predictions at 1 and 3 THz. The same property also allowed us to experimentally verify that the reflective biprism focus has a longitudinal extension much greater than that exhibited by a benchmark convex cylindrical mirror with the same optical power. The device is thermo-mechanically stable up to a heating power of 270 mW, although it might be potentially exploited at higher powers with minor degradation of the optical performances.

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Terahertz imaging in dielectric media with quasi-Bessel beams

Cited by 10 publications

References 11 publications

Submillimeter-Wave Cornea Phantom Sensing Over an Extended Depth of Field With an Axicon-Generated Bessel Beam

Submillimeter-Wave Cornea Phantom Sensing Over an Extended Depth of Field With an Axicon-Generated Bessel Beam

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

Long-Focusing Device for Broadband THz Applications Based on a Tunable Reflective Biprism

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