Fiber Coupled Transceiver with 6.5 THz Bandwidth for Terahertz Time-Domain Spectroscopy in Reflection Geometry

We present a fiber coupled transceiver head for terahertz (THz) time-domain reflection measurements. The monolithically integrated transceiver chip is based on iron (Fe) doped In0.53Ga0.47As (InGaAs:Fe) grown by molecular beam epitaxy. Due to its ultrashort electron lifetime and high mobility, InGaAs:Fe is very well suited as both THz emitter and receiver. A record THz bandwidth of 6.5 THz and a peak dynamic range of up to 75 dB are achieved. In addition, we present THz imaging in reflection geometry with a spatial resolution as good as 130 µm. Hence, this THz transceiver is a promising device for industrial THz sensing applications.

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Terahertz time-domain spectroscopy system using rhodium doped InGaAs antennas: 637 μW peak power and 110 dB dynamic range

2020 45th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) ◽

10.1109/irmmw-thz46771.2020.9370673 ◽

2020 ◽

Author(s):

Robert B. Kohlhaas ◽

Steffen Breuer ◽

Simon Nellen ◽

Lars Liebermeister ◽

Martin Schell ◽

...

Keyword(s):

Time Domain ◽

Peak Power ◽

Dynamic Range ◽

Terahertz Time Domain Spectroscopy ◽

Time Domain Spectroscopy ◽

Spectroscopy System

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Terahertz Time-Domain Polarimetry in Reflection for Film Characterization

Sensors ◽

10.3390/s20123352 ◽

2020 ◽

Vol 20 (12) ◽

pp. 3352

Author(s):

Sandrine van Frank ◽

Elisabeth Leiss-Holzinger ◽

Michael Pfleger ◽

Christian Rankl

Keyword(s):

Optical Properties ◽

Time Domain ◽

Terahertz Spectroscopy ◽

Single Layer ◽

Measured Signal ◽

Terahertz Time Domain Spectroscopy ◽

Wide Range ◽

Reflection Geometry ◽

Layer Thin Film ◽

Good Agreement

Terahertz time-domain spectroscopy is a useful technique to characterize layered samples and thin films. It gives access to their optical properties and thickness. Such measurements are done in transmission, which requires access to the sample from opposite sides. In reality this is not always possible. In such cases, reflection measurements are the only option, but they are more difficult to implement. Here we propose a method to characterize films in reflection geometry using a polarimetric approach based on the identification of Brewster angle and modeling of the measured signal to extract the refractive index and thickness of the sample. The technique is demonstrated experimentally on an unsupported single layer thin film sample. The extracted optical properties and thickness were in good agreement with established transmission terahertz spectroscopy measurements. The new method has the potential to cover a wide range of applications, both for research and industrial purposes.

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Terahertz Time-Domain Spectroscopy Based on Commercially Available 1550 nm Fabry–Perot Laser Diode and ErAs:In(Al)GaAs Photoconductors

Applied Sciences ◽

10.3390/app9132704 ◽

2019 ◽

Vol 9 (13) ◽

pp. 2704 ◽

Cited By ~ 2

Author(s):

Kai-Henning Tybussek ◽

Kevin Kolpatzeck ◽

Fahd Faridi ◽

Sascha Preu ◽

Jan C. Balzer

Keyword(s):

Laser Diode ◽

Time Domain ◽

Dynamic Range ◽

Laser System ◽

Industrial Applications ◽

Thz Radiation ◽

Full Potential ◽

Terahertz Time Domain Spectroscopy ◽

Time Domain Spectroscopy ◽

Fabry Perot

THz time-domain spectroscopy (TDS) is a promising tool for quality control purposes in industrial applications, but the high cost and the relatively large laser sources still make it difficult to use the full potential of the technology for a decent price. In this work, a THz TDS system, which uses a commercially available Fabry–Perot laser diode emitting at 1550 nm, is presented. By dispersion compensation, pulses with a duration of 544 fs were generated, resulting in THz radiation with a bandwidth of 1.4 THz and a peak dynamic range of 56 dB with state-of-the-art ErAs:In(Al)GaAs photoconducting antennas. These results are compared with those of a conventional and expensive fiber laser system with a 90 fs pulse duration.

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Ultra-High Repetition Rate Terahertz Time-Domain Spectroscopy for Micrometer Layer Thickness Measurement

Sensors ◽

10.3390/s21165389 ◽

2021 ◽

Vol 21 (16) ◽

pp. 5389

Author(s):

Kevin Kolpatzeck ◽

Xuan Liu ◽

Lars Häring ◽

Jan C. Balzer ◽

Andreas Czylwik

Keyword(s):

Time Domain ◽

Repetition Rate ◽

Dynamic Range ◽

Reference Signal ◽

Thickness Measurement ◽

Optical Signal ◽

High Repetition Rate ◽

Terahertz Time Domain Spectroscopy ◽

Time Domain Spectroscopy ◽

High Repetition

Terahertz time-domain spectroscopy systems driven by monolithic mode-locked laser diodes (MLLDs) exhibit bandwidths exceeding 1 THz and a peak dynamic range that can compete with other state-of-the-art systems. Their main difference compared to fiber-laser-driven systems is their ultra-high repetition rate of typically dozens of GHz. This makes them interesting for applications where the length of the terahertz path may not be precisely known and it enables the use of a very short and potentially fast optical delay unit. However, the phase accuracy of the system is limited by the accuracy with which the delay axes of subsequent measurements are synchronized. In this work, we utilize an all-fiber approach that uses the optical signal from the MLLD in a Mach–Zehnder interferometer to generate a reference signal that we use to synchronize the detected terahertz signals. We demonstrate transmission-mode thickness measurements of stacked layers of 17μm thick low-density polyethylene (LDPE) films.

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Application of Terahertz Spectroscopy and Imaging

Siberian Journal of Physics ◽

10.54362/1818-7919-2010-5-4-123-129 ◽

2010 ◽

Vol 5 (4) ◽

pp. 123-129

Author(s):

Mu Kaijun ◽

Zhang Cunlin

Keyword(s):

Time Domain ◽

Quartz Crystal ◽

Terahertz Spectroscopy ◽

Thz Radiation ◽

Radiation Polarization ◽

Air Plasma ◽

Thz Imaging ◽

Terahertz Time Domain Spectroscopy ◽

Security Applications ◽

Angle Of Rotation

We examined the feasibility of Terahertz time-domain spectroscopy (THz-TDS) using a 4-mm-thick quartz crystal to extract the angle of rotation of THz radiation polarization induced by a two-color laser in air plasma. We also used the THz-TDS technique to identify explosives and melamine in mixtures. In addition, we presented a new opto-mechanical scanner for security applications using the method of passive THz imaging

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Fastest Thickness Measurements with a Terahertz Time-Domain System based on Electronically Controlled Optical Sampling

Applied Sciences ◽

10.3390/app9071283 ◽

2019 ◽

Vol 9 (7) ◽

pp. 1283 ◽

Cited By ~ 8

Author(s):

Milad Yahyapour ◽

Angelika Jahn ◽

Katja Dutzi ◽

Thomas Puppe ◽

Patrick Leisching ◽

...

Keyword(s):

Time Domain ◽

Dynamic Range ◽

Signal To Noise Ratio ◽

Test Sample ◽

Thickness Measurement ◽

Terahertz Time Domain Spectroscopy ◽

Optical Sampling ◽

Contact Free ◽

Thickness Measurements ◽

Thickness Gauging

We apply a fast terahertz time-domain spectroscopy (TDS) system based on electronically controlled optical sampling (ECOPS) to contact-free thickness gauging. Our setup achieves a measurement speed of 1600 terahertz pulse traces per second, which—to our knowledge—represents the fastest thickness measurement performed with any terahertz system to-date. Using a silicon wafer as a test sample, we compare data of the ECOPS experiment to results obtained with a conventional terahertz TDS system and a mechanical micrometer gauge. We show that all systems provide consistent results within the measurement accuracy. Moreover, we perform thickness measurements of a rapidly moving sample and characterize the ECOPS setup with respect to time-domain dynamic range, signal-to-noise ratio, and spectral properties.

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