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Applied Sciences
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Terahertz and Far Infrared Pulsed Devices and Systems
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Terahertz and Far Infrared Pulsed Devices and Systems

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Optics and Lasers".

Deadline for manuscript submissions: closed (31 May 2019) | Viewed by 20495

Special Issue Editors

Prof. Dr. Sascha Preu

E-Mail Website
Guest Editor
Department of Electrical Engineering and Information Technology, Technical University of Darmstadt, Darmstadt, Germany
Interests: THz photomixers; THz photoconductors; field effect transistors; rectifiers; THz systems; THz spectroscopy; new materials for THz applications
Prof. Dr. Jan Balzer

E-Mail Website
Guest Editor
Faculty of Engineering, University Duisburg-Essen, Duisburg, Germany
Interests: THz systems; semiconductor lasers; THz spectroscopy; industrial applications for THz systems

Special Issue Information

Dear Colleagues,

Pulsed THz (100 GHz- 10 THz) and far infrared (FIR up to 30 THz) systems and devices have been, and still are, a major driver of the research field. As an example, a vast majority of broadband materials parameters data, such as of various plastics, semiconductors of various doping levels, liquids and more complex systems were determined by using pulsed systems, paving the way for realization of many components, devices and systems, as well as important applications. This Special Issue aims for providing an overview about latest research and developments of pulsed THz and FIR devices and systems. Areas of interest include (but are not limited to):

Recent developments of pulsed THz/FIR systems and components

  • Sources including (large area) photoconductive antennas, nonlinear crystals, quantum cascade lasers, optical parametric oscillators, free electron lasers, synchrotron radiation and pulsed electronic sources
  • System concepts such as asynchronous optical sampling (ASOPS), electronically controlled optical sampling (ECOPS), optical sampling by cavity tuning (OSCAT), air-biased coherent detection (ABCD) and air plasma generation
  • New materials and concepts for pulsed THz/FIR emitters and detectors, such as semiconductors modified or doped with functional materials, spintronic emitters, novel nonlinear crystal materials

Novel applications of pulsed THz/FIR systems

  • Non-destructive testing including thickness analysis
  • Broadband spectroscopy, algorithms for material parameter extraction
  • 2D and 3D hyperspectral imaging
  • Fundamental research including nonlinear effects in matter, solid state physics, high field experiments

Prof. Dr. Sascha Preu
Prof. Dr. Jan Balzer
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Applied Sciences is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Time domain spectroscopy
  • THz pulses
  • FIR pulses
  • High power
  • Non-destructive testing
  • Quantum cascade lasers
  • Free electron lasers
  • Synchrotron

Published Papers (5 papers)

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Research

9 pages, 3606 KiB  
Article
THz Superradiance from a GaAs: ErAs Quantum Dot Array at Room Temperature
by Weidong Zhang, Elliott R. Brown, Andrea Mingardi, Richard P. Mirin, Navid Jahed and Daryoosh Saeedkia
Appl. Sci. 2019, 9(15), 3014; https://doi.org/10.3390/app9153014 - 26 Jul 2019
Cited by 15 | Viewed by 2956
Abstract
We report that an ErAs quantum-dot array in a GaAs matrix under 1550 nm pulsed excitation produces cooperative spontaneous emission—Dicke superradiance—in the terahertz frequency region at room temperature. Two key points pertain to the experimental evidence: (i) the pulsed THz emission power is [...] Read more.
We report that an ErAs quantum-dot array in a GaAs matrix under 1550 nm pulsed excitation produces cooperative spontaneous emission—Dicke superradiance—in the terahertz frequency region at room temperature. Two key points pertain to the experimental evidence: (i) the pulsed THz emission power is much greater than the continuous wave (CW) photomixing power; and (ii) the ultrafast time-domain waveform displays ringing cycles. A record of ~117 μW pulsed THz power was obtained, with a 1550 nm-to-THz power conversion efficiency of ~0.2%. Full article
(This article belongs to the Special Issue Terahertz and Far Infrared Pulsed Devices and Systems)
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9 pages, 1638 KiB  
Article
Terahertz Time-Domain Spectroscopy Based on Commercially Available 1550 nm Fabry–Perot Laser Diode and ErAs:In(Al)GaAs Photoconductors
by Kai-Henning Tybussek, Kevin Kolpatzeck, Fahd Faridi, Sascha Preu and Jan C. Balzer
Appl. Sci. 2019, 9(13), 2704; https://doi.org/10.3390/app9132704 - 3 Jul 2019
Cited by 20 | Viewed by 4564
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Terahertz and Far Infrared Pulsed Devices and Systems)
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8 pages, 1417 KiB  
Communication
A Low-Cost Terahertz Camera
by François Blanchard, Joel Edouard Nkeck, Dominique Matte, Riad Nechache and David G. Cooke
Appl. Sci. 2019, 9(12), 2531; https://doi.org/10.3390/app9122531 - 21 Jun 2019
Cited by 9 | Viewed by 5243
Abstract
Cost effective imaging is required for a wide range of scientific and engineering applications. For electromagnetic waves in the terahertz (THz) frequency range, a key missing element that has prevented widespread applications in this spectral range is an inexpensive and efficient imaging device. [...] Read more.
Cost effective imaging is required for a wide range of scientific and engineering applications. For electromagnetic waves in the terahertz (THz) frequency range, a key missing element that has prevented widespread applications in this spectral range is an inexpensive and efficient imaging device. In recent years, vanadium oxide based thermal sensors have rapidly entered the market for night vision capability. At the same time, sensors based on this technology have been applied to the THz domain, but with two orders of magnitude larger pricing range. Here we show that, with a simple modification, a commercially available thermal imaging camera can function as a THz imaging device. By comparing a commercially available THz camera and this low-cost device, we identify the main sensitivity difference is not attributed to anything intrinsic to the devices, but rather to the analog-to-digital converter and dynamic background subtraction capability. This demonstration of a low-cost THz camera may aid in the rapid development of affordable THz imaging solutions for industrial and scientific applications. Full article
(This article belongs to the Special Issue Terahertz and Far Infrared Pulsed Devices and Systems)
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11 pages, 2757 KiB  
Article
Fastest Thickness Measurements with a Terahertz Time-Domain System Based on Electronically Controlled Optical Sampling
by Milad Yahyapour, Angelika Jahn, Katja Dutzi, Thomas Puppe, Patrick Leisching, Bernhard Schmauss, Nico Vieweg and Anselm Deninger
Appl. Sci. 2019, 9(7), 1283; https://doi.org/10.3390/app9071283 - 27 Mar 2019
Cited by 48 | Viewed by 4508
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Terahertz and Far Infrared Pulsed Devices and Systems)
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9 pages, 10989 KiB  
Article
Sub-Terahertz Computer Generated Hologram with Two Image Planes
by Mateusz Surma, Izabela Ducin, Przemyslaw Zagrajek and Agnieszka Siemion
Appl. Sci. 2019, 9(4), 659; https://doi.org/10.3390/app9040659 - 15 Feb 2019
Cited by 6 | Viewed by 2778
Abstract
An advanced optical structure such as a synthetic hologram (also called a computer-generated hologram) is designed for sub-terahertz radiation. The detailed design process is carried out using the ping-pong method, which is based on the modified iterative Gerchberg–Saxton algorithm. The novelty lies in [...] Read more.
An advanced optical structure such as a synthetic hologram (also called a computer-generated hologram) is designed for sub-terahertz radiation. The detailed design process is carried out using the ping-pong method, which is based on the modified iterative Gerchberg–Saxton algorithm. The novelty lies in designing and manufacturing a single hologram structure creating two different images at two distances. The hologram area is small in relation to the wavelength used (the largest hologram dimension is equivalent to around 57 wavelengths). Thus, it consists of a small amount of coded information, but despite this fact, the reconstruction is successful. Moreover, one of the reconstructed images is larger than the hologram area. Good accordance between numerical simulations and experimental evaluation was obtained. Full article
(This article belongs to the Special Issue Terahertz and Far Infrared Pulsed Devices and Systems)
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