Terahertz Imaging System Uses BWO As Source

http://mwrf.com/test-amp-measurement/terahertz-imaging-system-uses-bwo-source

An imaging system based on transmission and reflection modes in the terahertz region has been developed by using a backward-wave oscillator (BWO) as its source, a Golay-Cell as the detector, and an oscilloscope as a data acquisition unit.

Much research has shown that terahertz waves can penetrate a number of materials while generating images with high spatial resolution. A number of these terahertz imaging solutions rely on continuous-wave radiation sources like a backward-wave oscillator (BWO). BWOs offer high output power, good wave-front quality, working-wavelength tunability, and a high signal-to-noise ratio. At China’s Southeast University, a continuous-wave (CW) terahertz imaging system using a BWO as source, a Golay-Cell as a detector, and an oscilloscope as a data-acquisition unit has been developed by Gang Chen, Jie Pei, Fei Yang, Xiao Yang Zhou, Z.L. Sun, and Tie Jun Cui.

The system’s software, which is based on the oscilloscope, is designed to control object movement as well as the capture and display of continuous terahertz-wave image data. To show the system’s validity at room temperature, the team tested the imaging of different objects at 450 and 890 GHz. The system was affected by humidity, thickness, and material properties. In addition, imaging resolution was discovered to be better as incident frequency increased. The translation step also impacted imaging, showing that the appropriate frequency and translation step must be chosen to meet practical imaging requirements. See “Terahertz-Wave Imaging System Based On Backward Wave Oscillator,” IEEE Transactions On Terahertz Science And Technology, Sept. 2012, p. 504.

MIT develops terahertz laser the size of a comma

My note: This is translated from the Dutch, so I apologize about any errors, in the google translation
http://translate.google.com/translate?hl=en&sl=nl&u=http://www.delta.tudelft.nl/article/tiny-terahertz-laser-tamed/25971&prev=/search%3Fq%3Dmit%2Bdevelops%2Bterahertz%2Blaser%2Bsize%2Bcomma%26hl%3Den%26tbo%3Dd%26biw%3D1024%26bih%3D672%26site%3Dwebhp&sa=X&ei=R7i4UOmSG4eQ2AXM-IBw&ved=0CD4Q7gEwAg
A new MIT-produced terahertz laser, about the size of this comma, has been developed by PhD student Yuan Ren. His achievement signals a major step forward in the terahertz astronomy.

Terahertz radiation, wedged in-between far-infrared and microwave, has a growing number of applications ranging from airport security body scanners and medical imaging to the astronomy of the origin of stars and planets.

The main problem so far is the lack of suitable terahertz sources, says Dr.. Jian-Rong Gao from the Department of Quantum Nanoscience Within the Applied Sciences faculty and Ren's daily supervisor. Airport scanners Rely on microwave transmitters in the far gigahertz domain, which is a known and trusted technology, but at the expense of image resolution.

A CO2 laser can be used to generate terahertz radiation or verschillende, but it's a massive tool. And obviously not the first choice to put on board of a satellite or balloon-based astronomy mission.

Since about for years there's a new way of generating terahertz waves with a tiny structure on a chip, called a Quantum Cascade Laser. It has been produced by a team of researchers zoals Prof. Qing Hu from Massachusetts Institute of Technology in Boston and Dr.. John L. Reno from Sandia Labs in Albuquerque. And unless Dr. Gao is mistaken, we're about to hear far more from Quantum Cascade Lasers Often or QCL's in the near future.

The QCL itself is easy to overlook. The structure is a line of about a millimeter long and only 20 to 40 microns wide. Its height of about 10 microns is built up from alternating layers of two different semiconducting materials only a few nanometer high. Depositing alternating layers thesis takes about four hours.

The result is an artificial semiconductor structure All which does not exist in nature. The alternating layers of (aluminum) gallium arsenide create a structure with quantum wells, the energy levels or All which depend on the thickness of the layers. As an electron moves from one quantum well into the next generation rates and a terahertz photon, it will trigger a cascade of electrons and hence of THz photons.

So, QCLs are smart, tunable sources of terahertz radiation and tiny. What more can one ask for? Well, the output Should be high enough, the radiation Should be stable in both amplitude and frequency and it should preferably operate at room temperature.

Axis for the temperature: the QCL needs to be cooled to about minus 200 degrees Celsius (70 K) at All which point it consumes about 1 Watt and Produces 0.25 milliwatts output power, which is quite okay for terahertz astronomy. 

But cooling equipment needs All which in turn interferes with the laser's output. So, Ren, who got his MSc degree at the Purple Mountain Observatory of the Chinese Academy of Sciences had to find a way of stabilizing both amplitude and frequency of the QCL.

"This is a difficult problem," says Gao. "The laser only has one knob, so how do you control two different aspects?". The 'knob' that Gao refers to is the voltage-controlled small tuning range of the laser.

Nonetheless Ren succeeded in controlling both frequency and amplitude with a smart laboratory setup. He stabilized the laser's output by inserting a fast (up to 1 kHz) automatic diaphragm in the beam. A feedback mechanism controls the diaphragm to keep the beam at a pretty constant level.

Next was the feedback frequency. By comparing the QCL output with a fixed spectral line in methanol gas, Ren succeeded in converting frequency fluctuations into amplitude changes All which then were picked up by a detector and fed back to tune the QC laser.

By doing so, says his co-supervisor Dr. Gao, Ren has for the first time made a quantum cascade laser suitable for airborne or satellite terahertz astronomy. This is the field for All which Dr. Gao develops sensors That Are candidate for NASA space missions and balloon (see: TU develops Nasa mission detectors ). 

All set now? Not quite yet. Space engineers will have to find a way to pack Ren's laboratory set-up into the cramped confinements of the Gussto balloon-based telescope. And as far as the quantum cascade lasers are concerned: they'll have a bright future if they can be made to operate at room temperatures shall or close to it.

-> Yuan Ren, Super-heterodyne spectrometer using a terahertz quantum cascade laser, 4 December 2012, Prof. PhD supervisors. Teun Klapwijk and Prof. SC Shi, co-supervisor Dr.Jian-Rong Gao. Ren was supported by the joint PhD training program of the Academy and the Chinese Academy of Sciences (CAS). 

Manipulating Light with a Single Layer of Carbon

My Note: This is somewhat old, but I include it because it's from the source for the most popular blog post found on this blog: "Viewpoint: Stimulated Near-Infrared Light Emission in Graphene".

"Femtosecond Population Inversion and Stimulated Emission of Dense Dirac Fermions in Graphene"

 http://www.ameslab.gov/research/highlights/manipulating-light-single-layer-carbon

 T. Li, L. Luo, M. Hupalo, J. Zhang, M.C. Tringides, J. Schmalian, and J. Wang 

Researchers have shown that it may be possible to make lasers using single-layer sheets of carbon atoms — the novel material known as graphene. Lasers are made from materials that can absorb ordinary light and then emit photons that have matching waves to provide high intensity.To generate laser power, a material must first undergo a population inversion where an excess of electrons is excited. They must then produce optical gain when one photon is emitted spontaneously causing the excited state electrons to undergo a cascade reaction, each one emitting an additional photon coherent with the first, so a large intensity builds up. Graphene exhibits both of these properties. Very short light pulses, only a few femtoseconds (10^-15 seconds) in duration, were used to stimulate the graphene. Almost instantaneously broad population inversions were observed; and the ultrabroad band gain is established at about 10 femtoseconds, producing a much wider tuning range of light (from terahertz to ultraviolet) than in conventional lasing materials. This is remarkable for photonics materials. Comparison of the experiments with newly-developed theoretical approaches neatly explains the findings. This work opens up a wide range of possible uses of graphene in previously-unexplored areas, particularly ultra-fast telecommunications and laser technology.With graphene a little light may go a long way

Verisante Aura Named Finalist for 2013 SPIE Prism Award

http://finance.yahoo.com/news/verisante-aura-named-finalist-2013-184051879.html

VANCOUVER, BRITISH COLUMBIA--(Marketwire - Nov 20, 2012) - Verisante Technology, Inc. (TSX VENTURE:VRS)(VRSEF)(V3T.F) (the "Company" or "Verisante"), a leader in cancer detection technology, announced today that Verisante''s Aura™, the revolutionary skin cancer detection device, has been named a finalist for the 2013 Prism Awards in the Life Sciences and Biophotonics category.

"We are honoured to be a finalist for this prestigious Award," said Thomas Braun, President and CEO. "It is very gratifying to be recognized as an industry leader for our innovative and disruptive technology, which has the potential to improve patient outcomes, reduce wait times and also save the health care system time and money. The Aura is a game changing technology because in half a second it will tell doctors if a suspicious skin lesion is high or low risk for being cancerous and should be biopsied or not."
Verisante will be in attendance when the winner will be announced at the 2013 Prism Awards banquet on February 6 in San Francisco. The Verisante Aura™ beta units are currently installed at five leading dermatology clinics across Canada for software verification purposes. This is the final step prior to making this device available in Canada, 27 European countries, and Australia where the device has already been approved for sale. The Verisante Aura™ is expected to be commercially available in Canada, Europe and Australia in early 2013.
About the 2013 Prism Awards
The Prism Awards, named the "Photonics Oscar" by OptecNet Deutschland, is a celebration of the best of our industry. It takes place every year in conjunction with SPIE Photonics West in San Francisco, California.
The Prism Awards for Photonics Innovation is a leading international competition that honors the best new photonic products on the market. Over the years, the Prism Awards has received applications from more than 35 countries across the globe. Applications are judged by panel of leading industry experts, venture capitalists, luminaries and visionaries. The finalists and winners that are ultimately chosen (from General Electric, Agilent, Hamamatsu to Swamp Optics, Optotune, WiTec) reflect the diversity of the program.
SPIE Photonics West is the world''s largest and most influential photonics and optics event with over 1500 companies exhibiting and 20,000 attendees.
To find out more about the Awards, visit the website at http://www.photonicsprismaward.com.
About Verisante Technology, Inc.
Verisante is a medical device company committed to commercializing innovative systems for the early detection of cancer. The Verisante Aura™ for skin cancer detection and the Verisante Core™ series for lung, colon and cervical cancer detection utilize a proprietary cancer detection platform while the operating software and probe technology are unique to each device. The cancer detection platform was developed by the BC Cancer Agency and tested and refined at the Skin Care Centre at Vancouver General Hospital. This exclusive platform technology allows Verisante to develop and offer a range of compact, non-invasive cancer detection devices that offer physicians immediate results for many of the most common cancers. The Aura™ has been approved for sale in Canada, Europe and Australia. The Core™ has not yet been approved for sale.
Verisante Aura™ was awarded Popular Science Magazine''s "Best of What''s New Award" for 2011, and Verisante Core™ was named one of the top 10 cancer breakthroughs of 2011 by the Canadian Cancer Society. In addition, the Company was named a finalist for the 2011 Regional Awards for New Technology by the Canadian Manufacturers & Exporters and the National Research Council of Canada and named as the year''s top ranking Technology and Life Sciences Company on the TSX Venture 50.

USCD installs Teraview Spectra 3000

http://THzNetwork.net/index.php/archives/1666

A TeraView TPS Spectra 3000 system has been installed in the Infrared Laboratory for Novel Infrared and Magnetic Materials at the University of California, San Diego, founded and let by Professor Dimitri Basov. Professor Basov and his laboratory are world leaders in the use of optical and infrared methods to investigate the characteristic energies and physics of strongly correlated electron systems, magnetic semiconductors, superconductivity and other novel electromagnetic materials.

Prof Basov’s team will utilize the system for both routine characterisation of material systems at low temperatures, as well as a new project to develop a near-field microscopy system utilising terahertz time-domain techniques for spectroscopic measurements in ultra-high vacuum. TeraView has supplied a special breadboard version of its TPS Spectra 3000 time-domain terahertz spectrometer for the project.

Professor Basov is chair of the Department of Physics at the University of California at San Diego and has a long and substantive track record in the use of terahertz, infrared and optical methods applied to fundamental studies in condensed matter physics. He is a recipient of numerous prizes, including most recently the Frank Isakson Prize for Optical Effects in Solids from the American Physical Society in 2012.

This new project adds to TeraView’s growing installed base in the United States. Dr Don Arnone, TeraView’s CEO stated: ‘This collaboration with a prestigious research group highlights TeraView’s position as major supplier of terahertz systems and indicates the continued growth in the use of terahertz as a valuable tool for both fundamental physics as well as applications development in exciting areas such as terahertz microscopy’.

Abstract-Terahertz-bandwidth coherence measurements of a quantum dash laser in passive and active mode-locking operation

Eamonn Martin, Regan Watts, Laurent Bramerie, Alexandre Shen, Harry Gariah, Fabrice Blache, Francois Lelarge, and Liam Barry

http://www.opticsinfobase.org/ol/abstract.cfm?uri=ol-37-23-4967

This research carries out coherence measurements of a 42.7 GHz quantum dash (QDash) semiconductor laser when passively, electrically, and optically mode-locked. Coherence of the spectral lines from the mode-locked laser is determined by examining the radio frequency beat-tone linewidth as the mode spacing is increased up to 1.1 THz. Electric-field measurements of the QDash laser are also presented, from which a comparison between experimental results and accepted theory for coherence in passively mode-locked lasers has been performed.

Abstract-Extraordinary terahertz absorption bands observed in micro/nanostructured Au/polystyrene sphere arrays

http://www.nanoscalereslett.com/

Guotao Duan, Fuhai Su, Wen Xu, Cunlin Zhang and Weiping Cai

Terahertz (THz) time-domain spectroscopy is carried out for micro/nanostructured periodic Au/dielectric sphere arrays on Si substrate. We find that the metal-insulator transition can be achieved in THz bandwidth via varying sample parameters such as the thickness of the Au shell and the diameter of the Au/dielectric sphere. The Au/polystyrene sphere arrays do not show metallic THz response when the Au shell thickness is larger than 10 nm and the sphere diameter is smaller than 500 nm. This effect is in sharp contrast to the observations in flat Au films on Si substrate. Interestingly, the Au/polystyrene sphere arrays with a 5-nm-thick Au shell show extraordinary THz absorption bands or metallic optical conductance when the diameter of the sphere is larger than 200 nm. This effect is related to the quantum confinement effect in which the electrons in the structure are trapped in the sphere potential well of the gold shell.

OTST-2013 International Workshop on Optical Terahertz Science and Technology 2013

1st - 5th April 2013

Organization:

IEMN, Terahertz Photonics Group, Lille 1 University

Type:

Workshop

Venue:

Kyoto Terrsa

Location:

Shinmachi Kujo Minami-ku, Kyoto, Japan

Website:

OTST-2013 International Workshop on Optical Terahertz Science and Technology 2013

Area

Physical Sciences

Specialty

Physics

Subject

Optics/Lasers

Deadlines

• Abstract Deadline:
  30th November 2012

Speakers

Plenary & Invited Speakers

Mark Sherwin UC Santa Barbara, USA Alessandro Tredicucci Istituto Nanoscienze–CNR, Italy Biaobing Jin Nanjing University, China Carlo Sirtori Université Paris-Diderot, France Dave Cooke McGill University, Canada Jinghua Teng IMRE, Singapore Josef Fulop University of Pecs, Hungary Junichiro Kono Rice University, USA Keith Nelson Massachusetts Institute of Technology, USA Manfred Helm Helmholtz-Zentrum Dresden-Rossendorf, Germany Martina Havenith Ruhr- University Bochum, Germany M. Asada Tokyo Institute of Technology, Japan Naoki Oda NEC, Japan Paul Planken Delft University of Technology, Netherlands Richard Averitt Boston University, USA Sukhdeep Dhillon Ecole Normale Supérieure Paris, France T, Otsuji Tohoku University, Japan Thomas Elsaesser Max-Born-Institut, Germany T. Kiwa Okayama Univ, Japan Y. Kawano Tokyo Institute of Technology, Japan Yun-Shik Lee Oregon State University,USA

International Workshop on Terahertz Science and Technology 2013 (OTST2013) will be held in Kyoto, Japan April 1-5, 2013.

OTST2013 is part of a series of conferences held every two years. The previous four conferences have been held in Orlando, Florida, USA (2005, 2007) and Santa Barbara, California, USA (2009, 2011). The aim of this workshop is to foster discussion on the newest and most exciting research in the development and applications of terahertz instrumentation based on optical sources. Emphasis will be placed on sources and applications at wavelengths between 30 and 3000 microns (0.1-10 THz). In addition to the presentation of peer reviewed papers, we have added activities for students and newcomers, including atutorial session immediately before the conference begins (1 April, 2013). Please see the paper submission page for information on abstract submission.

Co-Chairs: Koichiro Tanaka (Kyoto University)
Masayoshi Tonouchi (Osaka University)

Contemporary scientific topics will be highlighted in areas such as:

- Terahertz pulse generation and detection
- Terahertz time-domain spectroscopy
- THz imaging and nondestructive evaluation
- THz near-field microscopy: developments and applications
- Nanotechnology impact on terahertz instrumentation
- Terahertz characterization of nanomaterials
- Time-resolved terahertz spectroscopy
- Probing ultrafast carrier dynamics and transport in materials
- Novel optical and material development: metamaterials and plasmonics
- Applications to molecular, biomolecular, and liquid phase spectroscopy
- Portal security applications
- Quantum cascade lasers
- Sources based on telecom pumps
- Emerging laser technology for use in optical THz sources and detectors
- Terahertz communications
- Terahertz waveguides
- LIDAR/DIAL system

Terahertz wafer scanner from ARP detects chip defects down to 1 nm

IMAGE: A terahertz scanner from Applied Research & Photonics (ARP) is able to scan the intricate patterns on a wafer undergoing the fabrication process for defects. (Courtesy ARP)
http://www.laserfocusworld.com/articles/2012/11/thz-wafer-scanner-arp.html

Harrisburg, PA--A terahertz wafer scanner from Applied Research & Photonics (ARP) detects chip defects down to 1 nm, decreasing rejects in wafer fabrication. ARP says that chip manufacturers face a daunting challenge of keeping the “rejects” down in the wafer fabrication process. While a blank wafer costs only a few hundred dollars, a processed wafer can be worth hundreds of thousands of dollars depending on the end product, tremendously increasing costs if the wafer is rejected towards the end of the fabrication process. To reduce wafer fab rejects, ARP has introduced a non-destructive sub-surface scanner with a resolution of 1 nm by using its continuous-wave (CW) terahertz technology.

In the inspection stage, a wafer is rejected when the accumulated number of defects on a wafer exceeds the prescribed limit. Unfortunately, ARP says the current state-of-the-art (SOTA) high-cost and high-sensitivity inspection machines available in the marketplace fail to detect defects that are hidden below layers. Consequently, a wafer may pass the inspection process, but the final device will fail because the inspection system was not able to detect the smaller and hidden defects. For example, says ARP, a SOTA inspection system that costs on the order of a million dollars has a resolution of 0.15 µm (150 nm) and will miss defects smaller than this size. As the modern fab process is defining feature sizes down to 60 nm or less, the fab inspection technicians are faced with the challenge of detecting and identifying defects that are only a few nanometers in diameter. ARP says it addresses this deficiency by introducing a terahertz scanner with a resolution of 1 nm.

Modern fab processes involve layer-by-layer construction and defining devices on a wafer (the so called bottom-up process) where tens of layers are stacked one on top of the previous. Common optical inspection system can see only on the surface and the resolution is limited. Thus, defects buried under the top surface must be detected early in the process before it progresses towards completion. This is not possible by instruments built around visible light or IR which is offered by the current SOTA.

Terahertz can penetrate most materials except metals; thus, it provides the opportunity to inspect not only the surface but also the sub-surface interior layers of a multi-layered substrate. Unlike X-ray, terahertz is non-ionizing; therefore, it does not perturb or damage delicate features which in some cases are only a few nanometers in size. The combination of terahertz properties and a smart positioning system incorporated in ARP’s terahertz inspection provides unique opportunity to successfully inspect wafers at early stage of defect formation as well as after-process device failure analysis. 

ARP is a dendrimer nanotechnology company with the core products in the terahertz area. ARP’s terahertz spectrometer, TeraSpectra (www.arphotonics.net), uses a high-power terahertz source enabling high-res resolution spectrometry in a 30 THz window for probing molecular phenomena on time scales from a few femtoseconds to a few tens of picoseconds.

SOURCE: ARP; http://terascanr.blogspot.com/2012/11/arp-deploys-terahertz-sub-surface.html

Abstract-Nanoplasmonic Terahertz Photoconductive Switch on GaAs

Barmak Heshmat , Hamid Pahlevaninezhad , Yuanjie Pang , Mostafa Masnadi Shirazi , Ryan B. Lewis , Thomas Tiedje , Reuven Gordon , and Thomas E. Darcie
http://pubs.acs.org/doi/abs/10.1021/nl303314a
Low-temperature (LT) grown GaAs has a sub-picosecond carrier response time that makes it favorable for terahertz photoconductive (PC) switching. However, this is obtained at the price of lower mobility and lower thermal conductivity than GaAs. Here we demonstrate sub-picosecond carrier sweep-out and over an order of magnitude higher sensitivity in detection from a GaAs-based PC switch by using a nanoplasmonic structure. As compared to a conventional GaAs PC switch, we observe 40 times the peak-to-peak response from the nanoplasmonic structure on GaAs. The response is double that of a commercial, antireflection coated LT-GaAs PC switch.

Abstract-Efficient terahertz electro-absorption modulation employing graphene plasmonic structures

http://arxiv.org/abs/1211.4176
 Berardi Sensale-Rodriguez, Rusen Yan, Mingda Zhu, Debdeep Jena, Lei Liu, Huili Grace Xing

We propose and discuss terahertz electro-absorption modulators based on graphene plasmonic structures. The active device consists of a self-gated pair of graphene layers, which are patterned to structures supporting THz plasmonic resonances. These structures allow for efficient control of the effective THz optical conductivity, thus absorption, even at frequencies much higher than the Drude roll-off in graphene where most previously proposed graphene-based devices become inefficient. Our analysis shows that reflectance-based device configurations, engineered so that the electric field is enhanced in the active graphene pair, could achieve very high modulation-depth, even ~100%, at any frequency up to tens of THz.

Samsung Galaxy S4 and iPhone 6 to Have Ability to See Through Walls?

A smartphone with the ability to see through objects.

http://www.christianpost.com/news/samsung-galaxy-s4-and-iphone-6-to-have-ability-to-see-through-walls-85520/

By Vincent Funaro , Christian Post Reporter

November 25, 2012|11:02 am

The Samsung Galaxy S4 and iPhone 6 might end up having the ability to see through walls with their cameras, according to a new report.

A research team at the University of Texas in Dallas has tapped into an unused range in the electromagnetic spectrum that could give smartphones this ability.

"We've created approaches that open a previously untapped portion of the electromagnetic spectrum for consumer use and life saving medical applications," said Dr. Kenneth O, professor of electrical engineering at UT Dallas.

This approach will allow images to be created with signals in the terahertz range without having to use several lenses inside a device.

When combined with CMOS (Complementary Metal-Oxide Semiconductor) technology, this ability could potentially be available on consumer devices such as computers, smartphones, and tablets.

"CMOS is affordable and can be used to make lots of chips," said Dr. O. "The combination of CMOS and terahertz means you could put this chip and a transmitter on the back of a cellphone, turning it into a device carried in your pocket that can see through objects."

Consumers would be able to use this technology in their cellphones to find studs in walls, or for the authentication of specific documents. Businesses would also be able to use it to find counterfeit money.

Terahertz can also be used for medical purposes as it can detect cancer tumors, diagnose diseases through breath analysis, and monitor the amount of toxins in the air.

"There are all kinds of things you could be able to do that we just haven't yet thought about," he continued.

And being that the iPhone and the Galaxy S lines are the top two smartphones in the market, they would probably be the first to receive this technology. Both the Galaxy S4 and iPhone 5S or 6 could be able to see through walls when they are released. However, it will probably take a little bit longer for consumers to get their hands on this groundbreaking technology.

Detective Work using Terahertz

http://www.fraunhofer.de/en/press/research-news/2012/november/detective-work-using-terahertz-radiation.html

It was a special moment for Michael Panzner of the Fraunhofer Institute for Material and Beam Technology IWS in Dresden, Germany and his partners: in the Dresden Hygiene Museum the scientists were examining a wall picture by Gerhard Richter that had been believed lost long ago. Shortly before leaving the German Democratic Republic the artist had left it behind as a journeyman's project. Then, in the 1960s, it was unceremoniously painted over. However, instead of being interested in the picture, Panzer was far more interested in the new detector which was being used for the first time here. Using it, the scientists gained important information about the layered structure of the wall and the structure of the picture area being examined. The joint project was sponsored by IWS, the Academy of Fine Arts Dresden [Hochschule für bildende Künste Dresden (HFBK)], the Research Institute for Monument Conservation and Archeometry [Forschungsinstitut für Denkmalpflege und Archäometrie (FIDA)] and the Technical University Dresden through the German Federal Ministry of Education and Research BMBF.

According to Panzer, the special thing about the terahertz (THz) scanner is that „In comparison with traditional processes, such as X-ray scanners, it works without causing any damage whatsoever. In addition, it does not require a special permit, as in the case of harmful X-rays. This is because the scanner only generates a radiated power of less than 1 µW. For comparison: under less than ideal conditions, cell phones emit up to 2 Watts. Furthermore the process, provides concrete data on the structure of the individual layers or of potential hollow areas. In this way the device also indicated in the Hygiene Museum that in one area the plaster on the wall had evidently been repaired - a valuable clue for the restorer.

The scientists used short electromagnetic pulses that penetrate the various materials almost without attenuation, whereby some materials display characteristic absorption lines, which can be used to identify them clearly. In previous tests, however, the system had reached its limits, for example with behind-the-wall paintings on uneven, very structured walls. For this reason the scientists at IWS continued to develop the detector head by modifying the THz optics together with the Fraunhofer Institute for Physical Measurement Techniques IPM. The application spectrum of the scanner was also expanded.

Caution, contaminated art

Currently, many museums cannot present valuable exhibits to the public because they are contaminated with biocides. The reason for this is that in the 1970s, with the best of intentions, antique textiles or wood sculptures were sprayed with pesticides to keep them from being destroyed. Today it is known that these agents are hazardous to health and a number of different measurement and decontamination processes are being tested. IWS, together with further partners, now wants to set up a project with the aim examining the possibilities and limits of the THz technology for organic biocides. „In contrast to the current X-ray fluorescence analysis which works on an element-selective basis, THz scanners recognize substances on the basis of the molecular bonding structure. Organic biocides, in particular, could be differentiated in such a manner," explains Michael Panzner.

To date, such expensive examinations are often only possible in well-equipped laboratories. In the future the tests are to be feasible on-site using a mobile scanner. However, a more research is still required until small, portable devices are available that are suitable for such purposes. Above all, close communication and cooperation with restorers and monument preservationists is required for the continued technological improvement of the THz measurement system. Panzner and his team are also hoping for a lively exchange at the European trade fair for monument preservation, restoration and refurbishment of old buildings, the denkmal, in Leipzig, Germany, where they will be exhibiting the new THz scanner generation in Hall 2, stand H30, from November 22 - 24, 2012.

Advanced Photonix makes advances with it's Terahertz applications the T-Gauge, F-35 product line, and moves it's anomaly detection system into non-airport market

My Note: On November 13th, 2012 Advanced Photonix held a conference call for listeners.
Here are some of the highlights:
The company announced that a record number of it's T-Gauge systems would be shipped in the 3rd Quarter for factory installation. COO Rob Risser indicated that API is beginning to get market traction in the industrial sensing sector with the early adopters of THz based sensing technology finding multiple uses for the T-Gauge. The company anticipates a steady growth of sales in the second half of the year.

CEO Rick Kurtz, indicated that the company is completing several F-35 contracts, (which appears to coincide with recent press about the delivery of the first F-35's to the Marines. http://www.sacbee.com/2012/11/20/5001044/lockheed-martin-delivers-three.html 
Rick also indicated that the goal is to fully commercialize the products which have been developed for use by API in the F-35 program for the companies domestic and international partners. 

Rob indicated that the companies anomaly detection system which it calls the Saf-T-Chek, has been evaluated by both the TSA, and In-Q-Tel, and was "well received". This month, the company is finalizing additional software improvements to the automated algorithm system, contained in the product, and anticipates that it will then be eligible to be placed on the intermodal transportation list, for use of the Saf-T-Chek, for a number of potential non-airport applications. It was interesting to hear that the company anticipates that FEMA will fund the development of this use. 

Use of the Saf-T-Chek, will requires a more rigorous qualification process before the product can be placed on the airport qualified equipment list, and is anticipated to be more than a year away. 

Overall, Rob expressed that the companies THz applications will be lower cost, and that the list of qualifed Value added resellers of the products continues to grow domestically and internationally, with an increasing sophistication in understanding how the companies THz applications are useful in  filling  a number of niche applications and markets.
 These of course, are my interpretations of what I heard listening to the conference call. Please listen for yourselves, to formulate your own understanding.

Physicists demonstrate crucial method for monitoring ultra short X-ray pulses

A single-cycle terahertz field accelerates photoelectrons emitted from neon atoms irradiated by an X-ray free-electron laser. In this way, the X-ray pulse temporal profile and arrival time are uniquely retrieved on a pulse-to-pulse basis with femtosecond precision. Credit: Jörg Harms/MPSD at CFEL
Read more at: http://phys.org/news/2012-11-physicists-crucial-method-ultra-short.html#jCp
http://phys.org/news/2012-11-physicists-crucial-method-ultra-short.html#jCp
With their ultra short X-ray flashes, free-electron lasers offer the opportunity to film chemical reactions or atoms in motion. However, for this super slow motion the arrival time and the temporal profile of the pulses must be precisely known. An international team of scientists has now developed a measurement technique that provides complete temporal characterization of individual FEL (free-electron laser) pulses at DESY´s soft-X-ray free-electron laser FLASH. The team, led by Adrian Cavalieri from the Center for Free-Electron Laser Science (CFEL) in Hamburg, was able to measure the temporal profile of each X-ray pulse with femtosecond precision (a femtosecond is a quadrillionth of a second). Their technique can be implemented at any of the world´s X-ray free-electron lasers, ultimately allowing for most effective utilization of these sources. The results are published in the current issue of the scientific journal Nature Photonics.

X-ray pulses delivered by free-electron lasers provide unique research opportunities, because the pulses are ultra-intense and ultra-short. At FELs trillions of X-ray photons are packed within a single burst – or pulse – which lasts for only several tens of femtoseconds, or even less. However, the precise arrival time and even the temporal profile of the FEL pulse can change dramatically from one pulse to the next.Therefore, to use the FEL to "film" ultrafast dynamical processes, the arrival time of each pulse must be measured to reorder the individual frames or snapshots captured with each individual FEL pulse. Provided with accurate timing information, femtosecond FEL X-ray pulses are short enough to study atoms in motion, chemical reactions, and phase transitions in materials with atomic resolution on the femtosecond timescale. With simultaneous measurement of the FEL X-ray pulse profile, it will be possible to go even further, to explore processes that evolve within the X-ray exposure. On these timescales the motion of electrons and electronic state dynamics become significant. Electronic dynamics drive damage processes in biomolecules, which may destroy them before they can be recorded in a crystal clear image. For their measurements, the team which includes scientists from CFEL, DESY, European XFEL, University of Hamburg and SLAC adapted a technique used in attosecond science called "photoelectron streaking" (an attosecond is a thousandth of a femtosecond). With this, the temporal profiles of varying light signals can be recorded. By taking advantage of the ultra-high intensities available at FELs the researchers were able to perform the streaking measurement on a single-shot basis at FLASH. For this, the X-ray flashes were shot through neon gas on their way to their target. Each pulse ejects a burst of photoelectrons from the noble gas. The temporal profile of the photoelectrons is a replica of the FEL pulse that ejected them. With an electromagnetic terahertz (THz) field, the photoelectrons are accelerated or decelerated, depending on the exact instant of their ejection. The strength of this effect is measured using time-of-flight spectroscopy. If the exact shape of the terahertz pulse is known, combining this information reveals the temporal profile and arrival time of the individual X-ray pulses with a precision of about 5 femtoseconds. "Simultaneous measurement of the arrival time and pulse profile, independent of all other FEL parameters, is the key to this technique," explains Cavalieri, who is a professor at the University of Hamburg and a group leader in the Max Planck Research Department for Structural Dynamics (MPSD). Until now, no other measurement has provided this complete timing information – yet it is exactly this information that will be crucial for future application of these unique X-ray light sources. The FEL pulse characterization measurements presented by the team are made without affecting the FEL beam – only a negligible number of photons are lost for creating photoelectrons. Therefore, they can be applied in any experiment at almost any wavelength, for example at the European XFEL which is currently under construction in Northern Germany. In the immediate future, laser-driven THz streaking will be used to monitor and maintain the FEL pulse duration at FLASH to study a wide variety of atomic, molecular and solid-state systems. For further experiments, the researchers plan to use these high precision measurements as critical feedback for tailoring and manipulating the X-ray pulse profile.
 More information: Grguras, I. et al., Ultrafast X-ray pulse characterization at free-electron lasers.
Nature Photonics, 2012 (advance online publication);
DOI: 10.1038/NPHOTON.2012.276
Journal reference: Nature Photonics