Broadband terahertz spectroscopy - a review paper

Broadband terahertz spectroscopy 

Wenhui Fan (范文慧)

Wenhui Fan, "Broadband terahertz spectroscopy (Invited Paper)," Chin. Opt. Lett. 9, 110008- (2011) 
http://www.opticsinfobase.org/col/abstract.cfm?URI=col-9-11-110008

Abstract

An overview of the major techniques to generate and detect THz radiation so far, especially the major approaches to generate and detect coherent ultra-short THz pulses using ultra-short pulsed laser, has been presented. And also, this paper, in particularly, focuses on broadband THz spectroscopy and addresses on a number of issues relevant to generation and detection of broadband pulsed THz radiation as well as broadband time-domain THz spectroscopy (THz-TDS) with the help of ultra-short pulsed laser. The time-domain waveforms of coherent ultra-short THz pulses from photoconductive antenna excited by femtosecond laser with different pulse durations and their corresponding Fourier-transformed spectra have been obtained via the numerical simulation of ultrafast dynamics between femtosecond laser pulse and photoconductive material. The origins of fringes modulated on the top of broadband amplitude spectrum, which is measured by electric-optic detector based on thin nonlinear crystal and extracted by fast Fourier transformation, have been analyzed and the major solutions to get rid of these fringes are discussed.

for more information about  the Spectra 3000 spectrometer click here

(http://www.teraview.com/products/terahertz-pulsed-spectra-3000/index.html)

Terahertz research in Spain (part 2) - (Campus Arrosadia 31006 Pamplona (Navarra) Spain)

(In spanish)

Laboratorio de TeraHercios

El laboratorio de Terahercios (THz) está compuesto por equipos de medida de altas prestaciones, para frecuencias del rango de THz. El principal equipo de medida es un espectrómetro de terahercios: TeraView TPS Spectra 3000.

Características del TeraView TPS Spectra 3000

• Este espectrómetro tiene un rango de medida o rango espectral de 0.06 THz - 4 THz, lo que equivalente a un rango de medida en longitud de onda de 2 cm-1 a 120 cm-1.
• Caracterización de muestras.
• Caracterización de materiales.
• Caracterización de compuestos:

• Farmacológicos
• Explosivos

• Microorganism Detection:

• Bacterias

• Pruebas y medidas no destructivas debidas a la transparencia de los THz a:

• Papel
• Materiales cerámicos
• Tejidos y materiales de la ropa
• Plásticos
• Madera

for more information click here

IMS2012 International Microwave Symposium (June 17-22, 2012)

WFC: Emerging Technology of Terahertz Imaging Systems, Devices, and Algorithms

Friday, 0800 – 1700

Sponsors: MTT-4

Organizers: 

Magda El-Shenawee, University of Arkansas, and Aly Fathy, University of Tennessee

Abstract: 

The rising interest in the terahertz band of frequency and the recent research in this area have motivated the organizers to foster an IMS workshop to address the state-of-the-art of this new technology. The goal of the proposed workshop is to addresses the recent research progress in terahertz systems, passive and active devices, sources, and imaging algorithms.

The workshop is related to Terahertz Technology and Applications (MTT-6) and Biological Effects and Medical Applications (MTT-10). It is also relevant to RF Nanotechnology (MTT-25), Microwave and Millimeter-Wave Integrated Circuits (MTT-6) and Microwave and Millimeter-Wave Solid State Devices (MTT-7).

The lack of inexpensive and efficient THz imaging systems is a main challenge that faces the advancement of THz research in potential applications from medical imaging to radar and communication systems. The workshop will discuss the state-of-the-art research in THz imaging radar systems, quantum cascade lasers, sources and detectors, surface plasmon based devices, low power sources, spectroscopy, biological sensing, chemical imaging, and pharmaceutical and medical applications. Recent applications of THz imaging include non-destructive evaluation, security screening, inspection of IC devices and packaging, detection of bio-threat, and cancer detection and assessment. THz tomography involves 3D reconstruction of unknown targets and their constitutive material properties. The workshop will discuss rigorous inverse scattering algorithms and the current challenges of available THz experimental data for the practical implementation.

1. “Novel Man-Engineered Bio-Nano-Materials for THz/IR-Based Sensing & Medical Applications” Dwight Woolard and James Jensen, U.S. Army Research Office
2. “Technology, Capabilities, and Performance of Low Power THz Sources” Goutam Chattopadhyay, NASA- Jet Propulsion Laboratbory
3. “Terahertz Chemical Imaging of Crystal Polymorphism for Pharmaceutical Applications” Katsushiro Ajito, NTT Microsystem Integration Labs
4. “High-performance THz Quantum Cascade Lasers and Applications” Qing Hu, MIT
5. “Terahertz Detection by Nanometer Field Effect Transistors: Physics and First Imaging Applications” Wojciech Knap and Domonique Coquilat, Université Montpellier
6. “Si-based Millimeter-Wave/THz Integrated Technologies” Safieddin Safavi, University of Waterloo
7. “THz Imaging Radar: Technology Development for Multi-pixel Multi-color architectures” Imran Mehdi and Peter Siegle, Jet Propulsion Laboratory
8. “Plasmonics for Imaging and Spectroscopy Between Radio and Light” Andrew Gallant and Martyn Chamberlain, Durham University
9. “Inverse Scattering Algorithms for Assessing Breast Tumor Margins using Terahertz Waves” Magda El-Shenawee and Ahmed Hassan, University of Arkansas

For more information see http://ims2012.mtt.org/en/Workshops/WFC

Effect of annealing on the temperature-dependent dielectric properties of LaAlO3 at terahertz frequencies

Xingquan Zou, Mi He, Daniel Springer, Dongwook Lee, Saritha K. Nair, Siew Ann Cheong, Tom Wu, C. Panagopoulos, D. Talbayev, and Elbert E. M. Chia

Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore 

Department of Physics and Engineering Physics, 2001 Percival Stern Hall, 6400 Freret street, New Orleans, Louisiana 70118, USA  

AIP Advances 2, 012120 (2012); http://dx.doi.org/10.1063/1.3679725

Abstract

We present THz conductivity of LaAlO3 (LAO) as a function of temperature and annealing, using terahertz time-domain spectroscopy (THz-TDS). We observed that, after annealing, spectral weight redistribution occurs, such that the real conductivity σ1(ω) changed from a featureless and almost frequency-independent spectrum, into one where peaks occur near the phonon frequencies. These phonon frequencies increase with increasing temperature. We attribute the appearance of these absorption peaks to the diffusion and relocation of oxygen vacancies. The dielectric functions of annealed LAO are well fitted with the Drude-Lorentz model.

from the paper

"........Our work fills this gap in knowledge, enabling future researchers to use the temperature-dependent refractive index of LAO to characterize their thin films more accurately. Here we report the temperature-dependent (10 K ‐ 300 K) dielectric response of LAO by terahertz time-domain spectroscopy (THz-TDS) from 0.2 THz − 3 THz. After annealing, strong absorption peaks appear in k(ω), with peak positions shifting to higher frequencies with increasing temperature.

Our investigated samples are single crystals of (100) LAO: a 10×10×1 mm³ piece from CrysTec GmbH (Berlin, Germany), and a 10×10×0.5 mm³ piece from SWI (Hsinchu, Taiwan). Since both samples give the similar results, we only show data from the CrysTec sample. The dielectric response of LAO was measured by a commercial THz-TDS system (TeraView Spectra 3000). .........."

For TeraView's full range of products see http://www.teraview.com/products/index.html 

Dielectric Spectroscopy for Soft Matter Research (Terahertz research in Spain part 1)

Written by Prof. Dr. Angel Alegria  who is the head of the Material Physics Department at University of the Basque Country, Spain in the European Soft Matter Infrastructure Newsletter

For more information click here (http://www.emat.ua.ac.be/ESMI_Newsletter.pdf)


The Dielectric Spectroscopy Laboratory (DSL) is one of the laboratories of the Material Physics Center (MPC), a joint research center set up in 2001 by the Univer- sity of the Basque Country (UPV/EHU) in collaboration with the Spanish National Research Council (CSIC).

Since then, the Polymers and Soft Matter Group (PSMG) laboratory has been further developed and upgraded in order to improve the quality of the different experimental set-ups and to facilitate the operation of the infrastructure by external users. The operative set-ups of DSL offer the unique possibility of performing high precision dielectric relaxation experiments over a huge range of frequencies (from 10^-5 to 3-10^10Hz, i.e. nearly 16 orders of magnitude).

Depending on the frequency range involved, these experiments can be carried out in different sample environments where temperature can be varied over a wide range (from 20 - 600 K) and pressure can be increased up to 300 MPa. Furthermore, the existing equipment allows experiments to be performed with simultaneous access to electric/dielectric and mechanical/rheological frequency dependent properties. The current range of instruments, listed in order offrequency range, are:

- Time-Domain Dielectric Spectrometer

- Broad-Band Dielectric Spectrometer

- High-Frequency Dielectric Spectrometer

- Micro-Wave Spectrometer

- Tera-Hertz Spectrometer

Technical details of the various instruments can be found on the ESMI website and at:

www.sc.ehu.es/sqwpolim/PSMG/dielab.html 

Most of the equipment uses widely-avai- lable software, and the temperature control systems are such that different set-ups do not generally involve specific training for each piece of equipment. In addition to the dielect- ric spectroscopy instruments, the infra- structure also provides several facilities for sample preparation and standard sample characterization (such as DSC, TGA, PVT, etc.). Details can be found at:

www.sc.ehu.es/sqwpolim/PSMG/infr.html

The scientists in charge of the various instruments are: Dr. Silvina Cerveny (Micro-Wave and Tera- Hertz spectrometers), Dr. Gustavo Schwartz (non-conventional sample environment), Dr. Silvia Arrese-Igor (Time-Domain and standard Dielectric Spectrometers).

For more information about  the Spectra 3000 terahertz spectrometer click here

or visit http://www.teraview.com/products/terahertz-pulsed-spectra-3000/index.html