Topography of hidden objects using THz digital holography with multi-beam interferences

Valzania, Lorenzo; Zolliker, Peter; Hack, Erwin

doi:10.1364/oe.25.011038

Cited by 42 publications

(15 citation statements)

References 23 publications

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“…This may pose a problem when laser stability is an issue. Unlike in-line [22,23] and off-axis [14,24] holography, ptychography requires no reference beam, making it possible to move a larger object closer to the detector and thus improving the lateral resolution. Moreover, ptychography can reconstruct objects larger than the beam diameter due to its moving field of view.…”

Section: Lettermentioning

confidence: 99%

Terahertz ptychography

Valzania¹,

Feurer²,

Zolliker³

et al. 2018

Opt. Lett.

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We realized a phase retrieval technique using terahertz (THz) radiation as an alternative to THz digital holography, named THz ptychography. Ptychography has been used in x-ray imaging as a groundbreaking improvement of conventional coherent diffraction imaging. Here we show that ptychography can be performed at THz frequencies too. We reconstructed an amplitude and a phase object with both simulated and real data. Lateral resolution accounts to <2λ, while depth variations as low as λ/30 can be assessed.

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Section: Lettermentioning

confidence: 99%

Terahertz ptychography

Valzania¹,

Feurer²,

Zolliker³

et al. 2018

Opt. Lett.

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“…One approach to avoid these problems is through the use of digital holography techniques, exploiting the coherent nature of the THz QCL source [39][40][41]. Unfortunately, the very nature of holographic imaging systems means that the fixed imaging field can be restrictive for noncooperative targets.…”

Section: Introductionmentioning

confidence: 99%

Coherent imaging using laser feedback interferometry with pulsed-mode terahertz quantum cascade lasers

Lim¹,

Bertling²,

Taimre³

et al. 2019

Opt. Express

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We report a coherent terahertz (THz) imaging system that utilises a quantum cascade laser (QCL) operating in pulsed-mode as both the source and detector. The realisation of a short-pulsed THz QCL feedback interferometer permits both high peak powers and improved thermal efficiency, which enables the cryogen-free operation of the system. In this work, we demonstrated pulsed-mode swept-frequency laser feedback interferometry experimentally. Our interferometric detection scheme not only permits the simultaneous creation of both amplitude and phase images, but inherently suppresses unwanted background radiation. We demonstrate that the proposed system utilising microsecond pulses has the potential to achieve 0.25 mega-pixel per second acquisition rates, paving the pathway to video frame rate THz imaging. Published by The Optical Society under the terms of the Creative Commons Attribution 4.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Using a THz QCL as an illumination source allows for higher resolution imaging than sub-THz systems (due to the shorter wavelength) and many orders of magnitude more power (> 100 mW) than typical time-domain systems [26]. Therefore, the THz QCL is emerging as an obvious

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“…While this property is also shared by microwaves, THz radiation provides a better spatial resolution thanks to the shorter wavelength, thereby imaging hidden objects with sub-millimeter resolution [3,4]. Experimental setups and techniques to image through THz-transparent materials have been put forward [5][6][7], allowing THz non-destructive inspection to gradually approach industrial use [8].…”

Section: Introductionmentioning

confidence: 99%

Coherent reconstruction of a textile and a hidden object with terahertz radiation

Valzania

Zolliker

Hack

2019

Optica

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Imaging through scattering materials is of utmost importance, especially for security and biomedical imaging. Unlike the rest of the electromagnetic spectrum, terahertz radiation is a non-ionizing probe and allows imaging deep through non-conducting materials with sub-millimeter resolution. Here, we propose a coherent imaging technique reconstructing two objects, hidden one behind the other, from relative shifts between them. Experimental reconstructions at λ 96.5 μm of amplitude and phase objects hidden behind a glass fabric sample are presented. The hidden objects are retrieved with a lateral resolution of ≈1.5λ and a depth resolution of ≈λ∕10. Besides envisioning its use in noninvasive imaging, we anticipate that, in selected applications, the suggested approach can replace a similar phase retrieval technique, namely ptychography.

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Topography of hidden objects using THz digital holography with multi-beam interferences

Cited by 42 publications

References 23 publications

Terahertz ptychography

Terahertz ptychography

Coherent imaging using laser feedback interferometry with pulsed-mode terahertz quantum cascade lasers

Coherent reconstruction of a textile and a hidden object with terahertz radiation

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