Interferometry-aided terahertz time-domain spectroscopy

Molter, Daniel; Trierweiler, Manuel; Ellrich, Frank; Jonuscheit, Joachim; Freymann, Georg von

doi:10.1364/oe.25.007547

Cited by 37 publications

(14 citation statements)

References 15 publications

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“…In addition to the shift, the visibility of the interference decreases when the PTFE plate is added due to Fresnel reflections at the surfaces. To determine the thickness of the plates, we estimated their refractive index using a standard time-domain spectroscopy (TDS) system (14) to be 1.42 ± 0.01. Knowing the refractive index and the shift of the interference signal allows for the calculation of the layer thickness.…”

Section: Resultsmentioning

confidence: 99%

Terahertz quantum sensing

et al. 2020

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Quantum sensing is highly attractive for accessing spectral regions in which the detection of photons is technically challenging: sample information is gained in the spectral region of interest and transferred via biphoton correlations into another spectral range, for which highly sensitive detectors are available. This is especially beneficial for terahertz radiation, where no semiconductor detectors are available and coherent detection schemes or cryogenically cooled bolometers have to be employed. Here, we report on the first demonstration of quantum sensing in the terahertz frequency range in which the terahertz photons interact with a sample in free space and information about the sample thickness is obtained by the detection of visible photons. As a first demonstration, we show layer thickness measurements with terahertz photons based on biphoton interference. As non-destructive layer thickness measurements are of high industrial relevance, our experiments might be seen as a first step towards industrial quantum sensing applications.

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Section: Resultsmentioning

confidence: 99%

Terahertz quantum sensing

et al. 2020

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“…If the time-base of the traces are not the same, averaging can degrade the spectral resolution, add undesirable artifacts to the spectrum, and decrease the sharpness of the resolved spectral lines. Again, an analogy can be made between this time-base distortion and the time-base distortion caused by the repeatability of delay stage positions in traditional THz-TDS systems 58 .…”

Section: Resultsmentioning

confidence: 99%

Self-triggered Asynchronous Optical Sampling Terahertz Spectroscopy using a Bidirectional Mode-locked Fiber Laser

Baker

Yardimci

et al. 2018

Sci Rep

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We report a self-triggered asynchronous optical sampling terahertz spectroscopy system based on a single bidirectional mode-locked fiber laser and plasmonics-enhanced photoconductive nanoantennas. The fiber laser generates two optical mutually coherent pulse trains with a stable repetition rate difference, enabling time-domain terahertz spectroscopy without using any mechanical delay line, stabilization electronics, or external trigger. The resolved terahertz spectra over a 0.1–2 THz frequency range and a 30-second measurement time show more than a 70-dB dynamic range, revealing water absorption lines matching the HITRAN database, through a light-weight and compact spectroscopy setup.

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“…The usability of robotic systems to bring the sensor to the device under test has been proven in the past [3,50]. The application of robots and the rough environment lead to the need of insensitivity to vibrations [51,52]. They can lead to severe disturbance of the acquired terahertz signal-especially when applying the most common TDS principle.…”

Section: Aspects Of Real-world Application In Production Environmentmentioning

confidence: 99%

Terahertz Quality Inspection for Automotive and Aviation Industries

Ellrich

Bauer

Schreiner

et al. 2019

J Infrared Milli Terahz Waves

135

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Nondestructive quality inspection with terahertz waves has become an emerging technology, especially in the automotive and aviation industries. Depending on the specific application, different terahertz systems-either fully electronic or based on optical laser pulses-cover the terahertz frequency region from 0.1 THz up to nearly 10 THz and provide high-speed volume inspections on the one hand and high-resolution thickness determination on the other hand. In this paper, we present different industrial applications, which we have addressed with our terahertz systems within the last couple of years. First, we show three-dimensional imaging of glass fiber-reinforced composites and foam structures, and demonstrate thickness determination of multilayer plastic tube walls. Then, we present the characterization of known and unknown multilayer systems down to some microns and the possibility of measuring the thickness of wet paints. The challenges of system reliability in industrial environments, e.g., under the impact of vibrations, and effective solutions are discussed. This paper gives an overview of state-of-the-art terahertz technology for industrial quality inspection. The presented principles are not limited to the automotive and aviation industries but can also be adapted to many other industrial fields.

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Interferometry-aided terahertz time-domain spectroscopy

Cited by 37 publications

References 15 publications

Terahertz quantum sensing

Terahertz quantum sensing

Self-triggered Asynchronous Optical Sampling Terahertz Spectroscopy using a Bidirectional Mode-locked Fiber Laser

Terahertz Quality Inspection for Automotive and Aviation Industries

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