Mail Inspection Based on Terahertz Time-Domain Spectroscopy

Molter, Daniel; Hübsch, Daniel; Sprenger, Thorsten; Hens, Korbinian; Nalpantidis, Konstantinos; Platte, Frank; Torosyan, G.; Beigang, R.; Jonuscheit, Joachim; Freymann, Georg von; Ellrich, Frank

doi:10.3390/app11030950

Cited by 6 publications

(4 citation statements)

References 21 publications

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“…This showed the high resolution of this experimental setup which is able to detect objects with a size below 1 mm. The high applicability of the terahertz waves in security was previously reported for the detection of weapons and explosives [13] or prohibited substances in the mail [14]. Świderski et al [1] presented the ability of THz waves to detect gun hidden behind clothes and water-filled cells in polymer samples.…”

Section: Resultsmentioning

confidence: 99%

The Terahertz-based non-destructive evaluation of military-designated materials

Strąg

Świderski²

2022

Emerging Imaging and Sensing Technologies for Security and Defence VII

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With regards to composite materials, the need for noninvasive evaluation of their structures, components, or systems they form continues to rise. It relates to the fact that composites, due to their two-phased (at least) composition, are vulnerable to different damages arising during their manufacturing or their use. Thus, there is a need to non-destructively monitor such materials especially when they are used in safety applications such as e.g., bulletproof vests and their damage may pose a real threat. In the frame of this work, the use of the newly developed non-destructive testing (NDT) method based on the application of Terahertz (THz) radiation was presented. For this purpose, the series of samples without defects and with a defect in their interior was investigated. The samples were prepared as the soft insert of a bulletproof vest and one of them had intentionally introduced defect in the form of aramid fibers textile soaked in salty water. The results obtained using the THz imaging method were compared to the ones obtained using the conventional X-ray method. Overall, the potential of THz transmission measurements was demonstrated and a selected application using THz-based system was presented.

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Section: Resultsmentioning

confidence: 99%

The Terahertz-based non-destructive evaluation of military-designated materials

Strąg

Świderski²

2022

Emerging Imaging and Sensing Technologies for Security and Defence VII

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“…Terahertz (THz)-wave technologies have been extensively studied for various applications [1][2][3][4] such as spectroscopic sensing, nondestructive imaging, and telecommunications. For these applications, various THz-wave generation methods have been developed.…”

Section: Introductionmentioning

confidence: 99%

Proposal and numerical verification of an ultrasmall terahertz source using integrated photonic crystal waveguides for highly efficient differential frequency generation

Koyama

Oda

Ikeda

et al. 2023

Jpn. J. Appl. Phys.

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We propose and numerically investigate integrated photonic crystal waveguides (PhC-WGs) formed in a semiconductor slab to realize an ultrasmall and highly efficient terahertz (THz) wave source. The structure consists of a straight PhC-WG with low-group-velocity and low-dispersion (LVLD) for efficient difference frequency generation (DFG) connected to two PhC-WGs to introduce two fundamental lights into the LVLD PhC-WG. The fundamental light propagating through each PhC-WG designed to enhance their electric fields by the slow-light effect is efficiently coupled to the LVLD PhC-WG owing to the reduced refractive index differences at the boundaries of the heterostructures. The DFG from the two fundamental lights was numerically simulated, and a temporal intensity oscillation corresponding to the difference in frequency was clearly observed. By comparing the DFG intensities of the integrated structures with an LVLD PhC-WG and a strip WG, the estimated DFG intensity from the LVLD PhC-WG was more than 100 times higher than that from the strip WG. These results indicate the effectiveness of the proposed heterostructure in the application of a highly efficient THz source with an ultrasmall footprint compared with conventional materials.

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“…The research of terahertz (THz) technologies provides fascinating paths for imaging [1][2][3][4][5] , biomedicine [6][7][8] , optical frequency combs [9,10] , communication [11,12] , and security diagnosis [1,13,14] . Thus, researches on strong and broadband THz emitters have earned considerable attentions [15] .…”

Section: Introductionmentioning

confidence: 99%

Spintronic terahertz emitter with integrated electromagnetic control

et al. 2022

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Spintronic thin films are considered as one of the promising terahertz (THz) source candidates, owing to their high performance and low cost. Much effort has been made to achieve spintronic THz sources with broadband and high conversion efficiency. However, the development of spintronic THz emitters with good compatibility, low cost, and miniaturized technology still faces many challenges. Therefore, it is urgent to extend commercial and portable spintronic THz emitters to satisfy many practical applications. Herein, we design a new generation of spintronic THz emitters composed of an alternating electromagnet and a miniaturized electronic controller. Not only can this new type of spintronic THz emitter largely simplify the ancillary equipment for spintronic sources, it also has a twice larger THz signal compared to the traditional THz time-domain spectroscopy systems with a mechanical chopper. Experimental results and theoretical calculations for electromagnetic coils show that our design can stably generate THz signals that are independent of the frequency and magnetic field of alternating signals. As the spin thin film is optimized, a magnetic field as low as 75 G satisfies the requirement for high performance THz emission. Hence, not only is the efficiency of the pump power enhanced, but also the driving current in the electromagnet is decreased. We believe that it has a wide range of applications and profound implications in THz technology based on spintronic emitters in the future.

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Mail Inspection Based on Terahertz Time-Domain Spectroscopy

Cited by 6 publications

References 21 publications

The Terahertz-based non-destructive evaluation of military-designated materials

The Terahertz-based non-destructive evaluation of military-designated materials

Proposal and numerical verification of an ultrasmall terahertz source using integrated photonic crystal waveguides for highly efficient differential frequency generation

Spintronic terahertz emitter with integrated electromagnetic control

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