Filters








33 Hits in 0.99 sec

High-power Lensless THz Imaging of Hidden Objects

Samira Mansourzadeh, Dilyan Damyanov, Tim Vogel, Frank Wulf, Robert B. Kohlhaas, Bjorn Globisch, Thorsten Schultze, Martin Hoffmann, Jan C. Balzer, Clara J. Saraceno
2021 IEEE Access  
The potential of pulsed THz radiation for time-of-flight imaging applications is well recognized. However, advances in this field are currently severely limited by the low average power of ultrafast THz sources. Typically, this results in impractically long acquisition times and a loss in resolution and contrast. These limitations make imaging of the objects in real-life scenarios impossible. Here, conclusively, the potential of state-of-the-art high-average power THz time-domain spectrometer
more » ... DS), driven by a 100-W class, one-box ultrafast oscillator for imaging applications is shown by demonstrating lensless THz imaging in reflection mode of a dielectric sample with low reflectivity. Images obtained with our home-built 20-mW average power THz-TDS system show a significant contrast enhancement compared to a state-ofthe-art commercial THz-TDS with less than 200 µW of average power. Our unique setup even allows us to obtain images of such an object with high-contrast hidden inside a medium-density fiberboard (MDF) box. This opens the door to THz time-of-flight imaging of concealed objects of unknown shape and orientation in various real-life scenarios which were so far impossible to realize. INDEX TERMS High-power terahertz radiation, lensless terahertz imaging, terahertz time-domain spectroscopy. 6268 This work is licensed under a Creative Commons Attribution 4.0 License. For more information, see https://creativecommons.org/licenses/by/4.0/ VOLUME 9, 2021
doi:10.1109/access.2020.3048781 fatcat:g7zygq4vhjgjrcdbpetleqjzyu

Optoelectronic frequency-modulated continuous-wave terahertz spectroscopy with 4 THz bandwidth

Lars Liebermeister, Simon Nellen, Robert B Kohlhaas, Sebastian Lauck, Milan Deumer, Steffen Breuer, Martin Schell, Björn Globisch
2021 Nature Communications  
Broadband terahertz spectroscopy enables many promising applications in science and industry alike. However, the complexity of existing terahertz systems has as yet prevented the breakthrough of this technology. In particular, established terahertz time-domain spectroscopy (TDS) schemes rely on complex femtosecond lasers and optical delay lines. Here, we present a method for optoelectronic, frequency-modulated continuous-wave (FMCW) terahertz sensing, which is a powerful tool for broadband
more » ... roscopy and industrial non-destructive testing. In our method, a frequency-swept optical beat signal generates the terahertz field, which is then coherently detected by photomixing, employing a time-delayed copy of the same beat signal. Consequently, the receiver current is inherently phase-modulated without additional modulator. Owing to this technique, our broadband terahertz spectrometer performs (200 Hz measurement rate, or 4 THz bandwidth and 117 dB peak dynamic range with averaging) comparably to state-of-the-art terahertz-TDS systems, yet with significantly reduced complexity. Thickness measurements of multilayer dielectric samples with layer-thicknesses down to 23 µm show its potential for real-world applications. Within only 0.2 s measurement time, an uncertainty of less than 2 % is achieved, the highest accuracy reported with continuous-wave terahertz spectroscopy. Hence, the optoelectronic FMCW approach paves the way towards broadband and compact terahertz spectrometers that combine fiber optics and photonic integration technologies.
doi:10.1038/s41467-021-21260-x pmid:33594078 fatcat:owig2lno55buxaq76rbn3gbiri

Influence of carrier lifetimes on the dynamical behavior of quantum-dot lasers subject to optical feedback

Björn Globisch, Christian Otto, Eckehard Schöll, Kathy Lüdge
2012 Physical Review E  
Globisch, K. Lüdge, and E. Schöll was supported by DFG in the framework of Sfb 787. C. Otto acknowledges the research training group GRK 1558 for support.  ... 
doi:10.1103/physreve.86.046201 pmid:23214657 fatcat:un7fehaahfahvoxvjhwxag7uva

Beam Profile Characterisation of an Optoelectronic Silicon Lens-Integrated PIN-PD Emitter between 100 GHz and 1 THz

Jessica Smith, Mira Naftaly, Simon Nellen, Björn Globisch
2021 Applied Sciences  
Knowledge of the beam profiles of terahertz emitters is required for the design of terahertz instruments and applications, and in particular for designing terahertz communications links. We report measurements of beam profiles of an optoelectronic silicon lens-integrated PIN-PD emitter at frequencies between 100 GHz and 1 THz and observe significant deviations from a Gaussian beam profile. The beam profiles were found to differ between the H-plane and the E-plane, and to vary strongly with the
more » ... mitted frequency. Skewed profiles and irregular side-lobes were observed. Metrological aspects of beam profile measurements are discussed and addressed.
doi:10.3390/app11020465 fatcat:5p6penczsvauri5mlo7o7o4cym

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

Robert B. Kohlhaas, Lars Liebermeister, Steffen Breuer, Marcel Amberg, David de Felipe, Simon Nellen, Martin Schell, Björn Globisch
2020 Sensors  
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
more » ... metry with a spatial resolution as good as 130 µm. Hence, this THz transceiver is a promising device for industrial THz sensing applications.
doi:10.3390/s20092616 pmid:32375349 fatcat:fcuqphq33fflfenwj35mgsjari

Second Harmonic Generation in Polymer Photonic Integrated Circuits

Hauke Conradi, Almontaserbillah Hakmi, Moritz Kleinert, Lars Liebermeister, David De Felipe, Madeleine Weigel, Martin Kresse, Crispin Zawadzki, Bjorn Globisch, Norbert Keil, Ronald Freund, Martin Schell
2020 Journal of Lightwave Technology  
Björn Globisch studied physics in Aachen, and Berlin, Germany, and received the diploma degree in physics from the Technische Universität Berlin, Berlin, in 2011, and the Ph.D. degree in physics from the  ... 
doi:10.1109/jlt.2020.3046371 fatcat:hp24dcgea5h7hlybxpwkglfvoa

Ultra-fast, High-Bandwidth Coherent cw THz Spectrometer for Non-destructive Testing

Lars Liebermeister, Simon Nellen, Robert Kohlhaas, Steffen Breuer, Martin Schell, Björn Globisch
2019 Journal of Infrared, Millimeter and Terahertz Waves  
Continuous wave THz (cw THz) systems define the state-of-the-art in terms of spectral resolution in THz spectroscopy. Hitherto, acquisition of broadband spectra in a cw THz system was always connected with slow operation. Therefore, high update rate applications like inline process monitoring and non-destructive testing are served by time domain spectroscopy (TDS) systems. However, no fundamental restriction prevents cw THz technology from achieving faster update rates and be competitive in
more » ... field. In this paper, we present a fully fibercoupled cw THz spectrometer. Its sweep speed is two orders of magnitude higher compared to commercial state-of-the-art systems and reaches a record performance of 24 spectra per second with a bandwidth of more than 2 THz. In the single-shot mode, the same system reaches a peak dynamic range of 67 dB and exceeds a value of 100 dB with averaging of 7 min, which is among the highest values ever reported. The frequency steps can be as low as 40 MHz. Due to the fully homodyne detection, each spectrum contains full amplitude and phase information. This demonstration of THz-spectroscopy at video-rate is an essential step towards applying cw THz systems in non-destructive, in line testing.
doi:10.1007/s10762-018-0563-6 fatcat:e2mwzmcwszbzbhu526cha6wmye

Beam Profile Investigation of an Optoelectronic Continuous-Wave Terahertz Emitter

Jess Smith, Simon Nellen, Sebastian Lauck, Bjorn Globisch, Mira Naftaly
2019 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz)  
Jess Smith 1,2 , Simon Nellen 3 , Sebastian Lauck 3 , Björn Globisch 3 , and Mira Naftaly 2 1 ATI, Surrey University, Guildford GU2 7XH, UK 2 National Physical Laboratory, Teddington TW11 0LW, UK 3 Fraunhofer  ... 
doi:10.1109/irmmw-thz.2019.8874086 fatcat:zszm624wm5hvffpofv2q3fmnze

Wireless THz link with optoelectronic transmitter and receiver [article]

Tobias Harter, Sandeep Ummethala, Matthias Blaicher, Sascha Muehlbrandt, Stefan Wolf, Marco Weber, Md Mosaddek Hossain Adib, Juned N. Kemal, Marco Merboldt, Florian Boes, Simon Nellen, Axel Tessmann (+5 others)
2019 arXiv   pre-print
Photonics might play a key role in future wireless communication systems that operate at THz carrier frequencies. A prime example is the generation of THz data streams by mixing optical signals in high-speed photodetectors. Over the previous years, this concept has enabled a series of wireless transmission experiments at record-high data rates. Reception of THz signals in these experiments, however, still relied on electronic circuits. In this paper, we show that wireless THz receivers can also
more » ... greatly benefit from optoelectronic signal processing techniques, in particular when carrier frequencies beyond 0.1 THz and wideband tunability over more than an octave is required. Our approach relies on a high-speed photoconductor and a photonic local oscillator for optoelectronic down-conversion of THz data signals to an intermediate frequency band that is easily accessible by conventional microelectronics. By tuning the frequency of the photonic local oscillator, we can cover a wide range of carrier frequencies between 0.03 THz and 0.34 THz. We demonstrate line rates of up to 10 Gbit/s on a single channel and up to 30 Gbit/s on multiple channels over a distance of 58 m. To the best of our knowledge, our experiments represent the first demonstration of a THz transmission link that exploits optoelectronic signal processing techniques both at the transmitter and the receiver.
arXiv:1901.03140v1 fatcat:un6becxg3rcmvg42p32zs5zx5i

COMPLEX DYNAMICS OF SEMICONDUCTOR QUANTUM DOT LASERS SUBJECT TO DELAYED OPTICAL FEEDBACK

CHRISTIAN OTTO, BJÖRN GLOBISCH, KATHY LÜDGE, ECKEHARD SCHÖLL, THOMAS ERNEUX
2012 International Journal of Bifurcation and Chaos in Applied Sciences and Engineering  
Globisch, K. Lüdge and E. Schöll was supported by DFG in the framework of Sfb 787. C. Otto would like to thank the research training group GRK 1558 for support. The work of T.  ... 
doi:10.1142/s021812741250246x fatcat:fmxg4g6mrvdn7jhz42xnnebjz4

Three-octave terahertz pulses from optical rectification of 20 fs, 1 μm, 78 MHz pulses in GaP

Jia Xu, Björn Globisch, Christina Hofer, Nikolai Lilienfein, Thomas Butler, Nicholas Karpowicz, Ioachim Pupeza
2018 Journal of Physics B: Atomic, Molecular and Optical Physics  
We demonstrate optical rectification of 1 μm pulses with a duration of 20 fs, a repetition-rate of 78 MHz and an average power of 5.5 W, in a 2 mm thick GaP crystal. The spectrum of the resulting far-infrared pulses is centered at 1.5 THz and extends to 5 THz at −50 dB intensity. In the absence of resonant absorption of GaP in this range, the spectrum has a well-behaved shape, facilitating spectroscopic applications. In the context of the recent rapid evolution of high-power Yb-based
more » ... laser systems, these results show a viable route towards sources of THz pulses combining broad bandwidth, high average power and a smooth spectral shape.
doi:10.1088/1361-6455/aacfe7 fatcat:4mmk4nihknfozlplrbidwpieom

Photoconductive Terahertz Emitters and Detectors for the Operation with 1550 nm Pulsed Fiber Lasers

Björn Globisch, Koch, Martin (Prof. Dr.)
2017
Björn Globisch, Roman J. B.  ...  First absolute terahertz power measurement of a time-domain spectroscopy system Björn Globisch, I.  ... 
doi:10.17192/z2017.0466 fatcat:pzw4aqspuna6plul2si7mipesu

THz Time-Domain Ellipsometer for Material Characterization and Paint Quality Control with More Than 5 THz Bandwidth

Helge Ketelsen, Rüdiger Mästle, Lars Liebermeister, Robert Kohlhaas, Björn Globisch, Technische Universität Berlin
2022
Quality control of car body paint in the automotive industry is a promising industrial application of terahertz technology. Terahertz time-domain spectroscopy in reflection geometry enables accurate, fast, and nondestructive measurement of individual layer thicknesses of multi-layer coatings. For high precision thickness measurements, the frequency dependent complex refractive index of all layers must be calibrated very accurately. THz time-domain ellipsometry is self-referencing and provides
more » ... liable, frequency resolved material properties with high signal-to-noise ratio. The method is characterized by a high sensitivity to optical material properties and layer thicknesses. We present characterization results in the frequency range 0.1–6 THz for typical automotive paints and different substrates such as polypropylene (PP), which features a high material anisotropy. We demonstrate that the broadband material properties derived from ellipsometry allow for inline thickness measurements of multi-layer car body paints with high accuracy.
doi:10.14279/depositonce-15637 fatcat:vk5p6rq5r5behkjxfxezuzd4yu

IEEE Transactions on Terahertz Science and Technology

2021 IEEE Transactions on Terahertz Science and Technology  
Gao Jiansong Gao Wei Jie Gao Luis Enrique Garcia Muñoz Frédéric Garet Andrew Gatesman Andrey Generalov Michael Gensch Deepu George Burak Gerislioglu Robert Giles Björn Globisch Mikhail Glyavin  ... 
doi:10.1109/tthz.2021.3089957 fatcat:zbjjmmkjzjddvgohziooai2kfm

IEEE Transactions on Terahertz Science and Technology

2021 IEEE Transactions on Terahertz Science and Technology  
Gao Jiansong Gao Wei Jie Gao Luis Enrique Garcia Muñoz Frédéric Garet Andrew Gatesman Andrey Generalov Michael Gensch Deepu George Burak Gerislioglu Robert Giles Björn Globisch Mikhail Glyavin  ... 
doi:10.1109/tthz.2020.3044141 fatcat:onx74ca5zbfolmkgytgh6vc46y
« Previous Showing results 1 — 15 out of 33 results