Terahertz: solutions looking for the right problems?

MY NOTE: I DON'T USUALLY INCLUDE pdf FILES AS STAND-ALONE POSTS, BUT THIS IS EXCELLENT AND VERY HELPFUL FOR THE LAY READER, LIKE ME.
http://www.etn-uk.com/Portals/0/Content/Terahertz/THz%2010/T01%20-Terahertz%20solutions%20looking%20for%20the%20right%20problems.pdf

THERE ARE SOME ERRORS IN THE CONTENTS, NOTABLY THE ASSERTION THAT PICOMETRIX IS A UK, COMPANY, AND THAT THERE AREN'T COMPACT THz UNITS ON THE MARKET TODAY. 

SIG Establishes Strategic Partnership with IQT

Image via Wikipedia

MY NOTE: THIS NEWS RELEASE DOESN'T DEAL DIRECTLY WITH TERAHERTZ, BUT SHOULD BE OF INTEREST TO MANY THAT FOLLOW THIS BLOG. IQT, WHICH IS AN OFFSHOOT OF THE CIA, IS PURSUING A VARIETY OF CUTTING EDGE TECHNOLOGIES WHICH FOCUS ON ENHANCING SECURITY. AS WAS PREVIOUSLY NOTED: 
"In November last year, In-Q-Tel invested in Advanced Photonix, the Michigan-based company that makes high-speed optical receivers for a variety of high-end applications including terahertz detection. Other investments include SpectraFluidics, a Californian start-up that specializes in surface-enhanced Raman spectroscopy (SERS) systems for security applications such as airport screening, and OpGen, which has developed an optical mapping system for genome analysis."

http://www.iqt.org/news-and-press/press-releases/2011/sig.html

March 30, 2011

Signal Innovations Group, Inc. (SIG), a leader in signal and image processing for defense and security, today announced a strategic investment and technology development agreement with In-Q-Tel, the independent strategic investment firm that identifies innovative technology solutions to support the missions of the U.S. Intelligence Community.
This strategic partnership between SIG and IQT will extend SIG's Intelligence, Surveillance, and Reconnaissance (ISR) technology development and provide new opportunities for SIG's product deployment. SIG's unique probabilistic framework sifts relevant data from the overwhelming volume of raw sensor data (pixels) to realize the full information potential from video systems. The company's data products include stabilized and georegistered imagery, vehicle and dismount tracks, traffic and behavior models, and analyst-aided-cueing for improved accuracy.
"Partnering with IQT helps us understand the system requirements and end-user needs for demanding video applications for security and intelligence," said Dr. Paul Runkle, CEO of SIG. "The insight provided by IQT's customers helps us drive technology innovation and product design for both commercial and government applications."
"SIG is a critical addition to our strategic investment portfolio and we are impressed with this technology's applicability to the challenges facing the Intelligence Community," said William Strecker, Executive Vice President and CTO at IQT. "SIG's video analytics technology offers unparalleled capabilities for extracting and representing relevant information in commercial and government video data."
Specific terms of the agreement were not disclosed.
About SIG
SIG is an emerging leader in signal, image, and video analytics for government and commercial applications. SIG's novel technology enables vast improvements in extracting relevant information from signals and imagery and making accurate decisions using this data. SIG's technology can utilize feedback from end-users to help the algorithms gain the benefit from human-aided decisions.
http://siginnovations.com/about-2/management-team/

Physicists Rotate Beams of Light in Terahertz domain

 

  

The magnetic field in the thin layer rotates the light waves. (Credit: Image courtesy of Vienna University of Technology)

http://www.sciencedaily.com/releases/2011/03/110330094149.htm
ScienceDaily (Mar. 30, 2011) — Controlling the rotation of light – this amazing feat was accomplished by means of a ultra thin semiconductor. This can be used to create a transistor that works with light instead of electrical current.

---

Light waves can oscillate in different directions -- much like a string that can vibrate up and down or left and right -- depending on the direction in which it is picked. This is called the polarization of light. Physicists at the Vienna University of Technology have now, together with researchers at Würzburg University, developed a method to control and manipulate the polarization of light using ultra thin layers of semiconductor material.
For future research on light and its polarization this is an important step forward -- and this breakthrough could even open up possibilities for completely new computer technology. The experiment can be viewed as the optical version of an electronic transistor. The results of the experiment have now been published in the journal Physical Review Letters.
Controlling light with magnetic fields
The polarization of light can change, when it passes through a material in a strong magnetic field. This phenomenon is known as the "Faraday effect." "So far, however, this effect had only been observed in materials in which it was very weak," professor Andrei Pimenov explains. He carried out the experiments at the Institute for Solid State Physics of the TU Vienna, together with his assistant Alexey Shuvaev. Using light of the right wavelength and extremely clean semiconductors, scientists in Vienna and Würzburg could achieve a Faraday effect which is orders of magnitude stronger than ever measured before.
Now light waves can be rotated into arbitrary directions -- the direction of the polarization can be tuned with an external magnetic field. Surprisingly, an ultra-thin layer of less than a thousandth of a millimeter is enough to achieve this. "Such thin layers made of other materials could only change the direction of polarization by a fraction of one degree," says professor Pimenov. If the beam of light is then sent through a polarization filter, which only allows light of a particular direction of polarization to pass, the scientists can, rotating the direction appropriately, decide whether the beam should pass or not.
The key to this astonishing effect lies in the behavior of the electrons in the semiconductor. The beam of light oscillates the electrons, and the magnetic field deflects their vibrating motion. This complicated motion of the electrons in turn affects the beam of light and changes its direction of polarization.
An optical transistor
In the experiment, a layer of the semiconductor mercury telluride was irradiated with light in the infrared spectral range. "The light has a frequency in the terahertz domain -- those are the frequencies, future generations of computers may operate with," professor Pimenov believes. "For years, the clock rates of computers have not really increased, because a domain has been reached, in which material properties just don't play along anymore." A possible solution is to complement electronic circuits with optical elements. In a transistor, the basic element of electronics, an electric current is controlled by an external signal. In the experiment at TU Vienna, a beam of light is controlled by an external magnetic field. The two systems are very much alike. "We could call our system a light-transistor," Pimenov suggests.
Before optical circuits for computers can be considered, the newly discovered effect will prove useful as a tool for further research. In optics labs, it will play an important role in research on new materials and the physics of light.

New Laser Technology Aims to Revolutionize Communications

Monday, March 28, 2011

(Photo: Patryk Buchcik/MorgueFile)
http://www.labspaces.net/109845/Modulating_frequency_and_amplitude_in_laser_light_leads_to_clear__ultrafast_free_space_communications

As fiber optic technology continues to advance, it faces challenges from both its physical properties and its use of infrastructure. One emerging high-speed solution being developed at Stevens Institute of Technology uses lasers to transmit data through readily available open space, with the potential of expanding past the limitation of fibers into a system known as optical free space communications. Dr. Rainer Martini has overcome a number of free space challenges to develop a high-speed communications technology that is not limited by a physical conductor. With an optical system that is stable enough, satellites may one day convert to laser technology, resulting in a more mobile military and super-sensitive scanners, as well as faster Internet for the masses.
A paper explaining the work, "Optically induced fast wavelength modulation in a quantum cascade laser," was recently published in Applied Physics Letters. The paper was later featured in the research highlights of Nature Photonics. In addition, Laser Focus World Magazine created a feature news story on the results for its November issue.
Director of Stevens Ultrafast Laser Spectroscopy and Communication Laboratory and Associate Professor of Physics and Engineering Physics, Dr. Martini hopes to extend the reach into the terahertz spectrum. But first he and his team faced a fundamental problem: optically-induced modulation of lasers.
A laser's beam must be optically modulated in order to transmit large amounts of data. Optically-induced amplitude modulation (AM) of mid-infrared lasers was realized by researchers at Stevens a few years ago, but AM signals are at the mercy of dust and fog. Now, Stevens researchers led by Dr. Martini have developed a technique to optically modulate the frequency of the beam as well (frequency modulation; FM) – resulting in a signal that is disrupted significantly less by environmental factors. The new research stands to revolutionize communications, rendering environmental barriers meaningless and allowing mobile units not tied to fiber optic cable to communicate in the range of 100 GHz and beyond, the equivalent of 100 gigabytes of data per second.
Electronic modulation of middle infrared quantum cascade laser is limited to 10 GHz, and optical modulation of frequency and amplitude offers a viable alternative. Last year, Martini and his team at Stevens, The Innovation University™, developed a method to optically induce fast amplitude modulation in a quantum cascade laser - a process that allows them to control the laser's intensity. Their amplitude modulation system employed a second laser to modulate the amplitude of the middle infrared laser – in essence using light to control light. But the team still faced the problem of reliability, so they turned to optical frequency modulation. "FM transmitted data is not affected by the environmental elements that affect AM data," Martini says. The recent success allows modulating specifically the emission frequency of the laser – allowing a much more reliable transmission. "But," Martini qualifies, "This was much more difficult to achieve and to prove."
Their optical approach has a number of applications, including frequency modulation in a middle infrared free space communications system, wavelength conversion that will transform a near infrared signal directly into a middle infrared signal, and frequency modulation spectroscopy.
"Dr. Martini's creativity and persistence have yielded great advances in laser optics," says Dr. Michael Bruno, Dean of the Charles V. Schaefer, Jr. School of Engineering and Science. "As the first person to explore amplitude and frequency modulation, he opened the doors to faster, clearer, free space communications. Today, he continues to advance a field he created."
As pioneers into the evolving world of free-space optical communications, Dr. Martini and his team continue to search for new solutions in translating research into every-day reality. One area of focus could take the lasers below ground by integrating the system into existing fiber optics networks, enabling high speed laser communications both above and below ground. The team is also developing a phase control detector to complement their recently-created phase control emitter, which will create an entirely phase-controlled system, and enable researchers to manage every aspect of the system. Such a control is well know from radar and radio systems – yet unprecedented in optical systems. This could open a whole new world of possibilities including enhanced chemical and biological detection by up to 1,000,000 times, and facilitate integration into products.
For Dr. Martini, it is all a matter of perseverance as he explores this new frontier. "There is proof of concept that we can do it," Martini says. "The question now is what limitations are there?"
 
###
Stevens Institute of Technology: http://www.stevens.edu

Chemist develops technique to use Terahertz to predict molecular crystal structures

Image via Wikipedia

http://chemistrynewsarticles.blogspot.com/2011/03/chemist-develops-technique-to-use-light.html

A Syracuse University chemist has developed a way to use very low frequency light waves to study the weak forces (London dispersion forces) that hold molecules together in a crystal. This fundamental research could be applied to solve critical problems in drug research, manufacturing and quality control.

The research by Timothy Korter, associate professor of chemistry in SU's College of Arts and Sciences, was the cover article of the March 14 issue of Physical Chemistry Chemical Physics. 

"When developing a drug, it is important that we uncover all of the possible ways the molecules can pack together to form a crystal," Korter says. "Changes in the crystal structure can change the way the drug is absorbed and accessed by the body."

One industry example is that of a drug distributed in the form of a gel capsule that crystallized into a solid when left on the shelf for an extended period of time, Korter explains. The medication inside the capsule changed to a form that could not dissolve in the human body, rendering it useless. The drug was removed from shelves. This example shows that it is not always possible for drug companies to identify all the variations of a drug's crystal structure through traditional experimentation, which is time consuming and expensive.

"The question is," Korter says, "can we leverage a better understanding of London and other weak intermolecular forces to predict these changes in crystal structure?"

Korter's lab is one of only a handful of university-based research labs in the world exploring the potential of THz radiation for chemical and pharmaceutical applications. THz light waves exist in the region between infrared radiation and microwaves and offer the unique advantages of being non-harmful to people and able to safely pass through many kinds of materials. THz can also be used to identify the chemical signatures of a wide range of substances. Korter has used THz to identify the chemical of signatures of molecules ranging from improvised explosives and drug components to the building blocks of DNA.

Korter's new research combines THz experiments with new computational models that accurately account for the effects of the London dispersion forces to predict crystal structures of various substances. London forces are one of several types of intermolecular forces that cause molecules to stick together and form solids. Environmental changes (temperature, humidity, light) impact the forces in ways that can cause the crystal structure to change. Korter's research team compares the computer models with the THz experiments and uses the results to refine and improve the theoretical models.

"We have demonstrated how to use THz to directly visualize these chemical interactions," Korter says. "The ultimate goal is to use these THz signatures to develop theoretical models that take into account the role of these weak forces to predict the crystal structures of pharmaceuticals before they are identified through experimentation."

A National Science Foundation Early Career Development (CAREER) Award funds Korter's research.

Story Source:

The above story is reprinted (with editorial adaptations) from materials provided by Syracuse University.

Photonics Is Becoming A Key Security Technology

Image via Wikipedia

http://www.photonicsonline.com/article.mvc/Photonics-Is-Becoming-A-Key-Security-0001?atc~c=771+s=773+r=001+l=a

March 22, 2011

LASER World of PHOTONICS 2011 will showcase Security and Defense applications
Security and defensLASER World of PHOTONICS 2011e has become one of the world's greatest twenty-first century challenges. The rapid development of optical technologies in the last few years have made possible many modern security and defense products that were previously impossible.
Recognizing this trend, LASER World of PHOTONICS 2011 has established "Security and Defense" as a separate exhibition area. There, manufacturers of both civil and military security systems, as well as systems and plant manufacturers and raw material suppliers will exhibit applications used for monitoring and recognizing objects and people, detecting hazardous substances or optimizing production processes. Within this themed area, companies and scientists will be able to exchange application-related experience and information on issues concerning security and defense.
Johannes Dumanski from Qioptiq Photonics GmbH & Co. KG, a leading security and space travel photonics component manufacturer, commented on the emergence of this market segment: "The 'asymmetric' threat, which has been noticeable for many years, is forcing security and defense firms to examine new scenarios. This is necessary both in preventive and reactive terms. In order to cope more easily with the tasks, greater use is being made of optical products and technologies both within the meaning of cross-sectional improvement of equipment standards and in regard to technical specialization."
Laser-based surveillance technologies are extremely important for domestic security, terrorism prevention and monitoring refugee movement. New products at the trade fair will include cameras in the Short Wave Infrared Range (SWIR), an underutilized wavelength range between 900 and 1900 nanometers, which are able to better recognize objects.LASER World of PHOTONICS 2011
Night sight and thermal imaging devices are also improving with the newer technology. "The new laser night sight brighteners in Laser Class 1 give our police officers much more security during operations at night. Based on the high wavelength of around 1000 nm, the laser beam is completely invisible to the normal observer. However, it illuminates a cone with a diameter of 26 meters for clear recognition at a distance of 1000 meters", explained David Heckner from Laserluchs GmbH. This product will be exhibited on Booth 152 in Hall C1.
Improved fiber-optic sensor systems for property protection
Fiber-optic sensor systems provide solutions to increasingly more complex problems. Optical and photoacoustic motion detectors are used to monitor borders, enclosures, tunnels and hundreds of miles of pipelines. The sensors in these systems transmit accurate information about every movement on the monitored object and store an acoustic fingerprint of the intruder.
Jakob Skov, Managing Director of NKT Photonics A/S (Hall B1, Booth 461), describes the efficiency and future potential of the laser technology used for this purpose: "Ultra-low-noise fiber lasers from the KOHERAS model series with coherence lengths well over 100 kilometres increase detection and localization accuracy and extend the measuring distance in fiber-optic sensor systems, thus significantly overcoming conventional laser. The present and future extent of these security-related markets will produce additional growth potential for our industrial fiber laser products in the sensing sector."
Civil use of fiber-optic sensor systems
The Security and Defense focus area will also feature the civil use of fiber-optic sensor systems, including applications for minimizing underground mining risks or monitoring the load in wind farms. Other featured products include new 3-D scanners and innovative production line quality assurance technologies. The innovation drivers in this sector are the still very young terahertz technology and new processes for laser spectroscopy and imaging. Eight Fraunhofer institutes will present future-oriented applied research results relating to this topic on a joint stand in Hall B2 (Booth 417).
About LASER World of PHOTONICS
LASER World of PHOTONICS is regarded as the home base of the photonics industry. According to a survey conducted by Infratest, 98% of exhibitors and 97% of visitors were extremely satisfied with the trade fair and intend to return in 2011. In addition to business objectives, the cultivation of contacts in the industry plays a very important role for all participants.
This year will feature four focus topics "Lasers and Laser Systems in Production", "Green Photonics", "Biophotonics and Life Sciences" and "Security and Defense".
LASER World of PHOTONICS has been held every two years since 1973. In 2009 it attracted 1,034 exhibitors and 25,365 visitors. The number of exhibitors and visitors from outside Germany has risen continuously and is presently 57% for exhibitors and 51% for visitors.
A sister event, LASER World of PHOTONICS China, is the leading regional trade show for optical technologies in China. It takes place in Shanghai March 15-17, 2011.
Claudia Sixl, Project Group Leader for LASER World of PHOTONICS at Messe München, explains the special nature of this event: "Due to the close connection between industry and research at an international level and the fact that LASER World of PHOTONICS covers the entire spectrum of optical technologies from components and systems through to application areas, we offer unique advantages. These advantages have become indispensable in a tough competitive environment with which our customers are now faced. This fact is also recognized by all the leading names in the industry through their attendance at LASER World of PHOTONICS."
For more information, visit www.world-of-photonics.net/en
Please order your tickets online (http://world-photonics.net/en/laser/visitors/prices-tickets)
About the World of Photonics Congress
The World of Photonics Congress, Europe's largest photonics conference, is organized with the cooperation of the world's leading photonics organizations. This conference will be held May 22 to 26, 2011, concurrently with the LASER World of PHOTONICS trade fair. The World of Photonics Congress conferences include:

• CLEO/Europe-EQEC, organized by the European Physical Society (EPS)
• Optofluidics and Manufacturing of Optical Components, organized by the European Optical Society (EOS)
• LIM - Lasers In Manufacturing, organized by the Scientific Laser Society (WLT)
• ECBO-European Conference on Biomedical Optics, organized by SPIE and the Optical Society of America (OSA)
• Optical Metrology, organized by SPIE Europe
• Application Panels - practical applications of lasers and photonics, organized by Messe München.

The program will also include conferences and events on material processing topics such as the "Lasers in Manufacturing" Conference (LIM 2011), which is being organized by the German Scientific Laser Society (Wissenschaftliche Gesellschaft für Lasertechnik e.V. (WLT)).
The Congress program will include a new event, "Optofluidics", organized by the European Optical Society (EOS). The Optical Metrology Conference includes a new subconference, "Videometrics" in addition to its traditional program contents. For more information, visit: www.photonics-congress.com.
About Messe München International
Messe München International (MMI) is one of the world's leading trade-fair companies. It organizes around 40 trade fairs for capital and consumer goods, and key high-tech industries. Each year over 30,000 exhibitors from more than 100 countries, and over two million visitors from more than 200 countries take part in the events in Munich. In addition, MMI organizes trade fairs in Asia, Russia, the Middle East and South America. Via its six subsidiaries - in Europe and in Asia - and 64 foreign representatives actively serving over 90 countries, MMI has a worldwide business network. Environmental protection and sustainability are key priorities in all MMI´s operations, at home and abroad. For more information, visit: www.messe-muenchen.com.
With a combined total of 1,300 exhibitors and more than 50,000 visitors in Munich and Shanghai, Messe München International is one of the world's leading trade show organizers for lasers and photonics. The World of Photonics websites at www.world-of-photonics.net/en offer information on the photonics trade shows, industry information, market data, details on product innovations, and application reports.
SOURCE: LASER World of PHOTONICS 2011 

Process Gives Graphene Nanoribbons Metallic Properties

Image via Wikipedia

Released: 3/18/2011 4:30 PM EDT

MY NOTE: THIS STORY IS NOT DIRECTLY ABOUT TERAHERTZ, BUT SHOULD BE OF INTEREST TO READERS OF THIS BLOG, FOR A VARIETY OF REASONS. IT MAY NOT DIRECTLY RELATE TO THz, TODAY, BUT IT MAY TOMORROW.

http://www.newswise.com/articles/view/574582/?sc=rssn

Source: Georgia Institute of Technology, Research Communications

Newswise — A new “templated growth” technique for fabricating nanoribbons of epitaxial graphene has produced structures just 15 to 40 nanometers wide that conduct current with almost no resistance. These structures could address the challenge of connecting graphene devices made with conventional architectures – and set the stage for a new generation of devices that take advantage of the quantum properties of electrons.

“We can now make very narrow, conductive nanoribbons that have quantum ballistic properties,” said Walt de Heer, a professor in the School of Physics at the Georgia Institute of Technology. “These narrow ribbons become almost like a perfect metal. Electrons can move through them without scattering, just like they do in carbon nanotubes.”

De Heer was scheduled to discuss recent results of this graphene growth process March 21st at the American Physical Society’s March 2011 Meeting in Dallas. The research was sponsored by the National Science Foundation-supported Materials Research Science and Engineering Center (MRSEC).

First reported Oct. 3 in the advance online edition of the journal Nature Nanotechnology, the new fabrication technique allows production of epitaxial graphene structures with smooth edges. Earlier fabrication techniques that used electron beams to cut graphene sheets produced nanoribbon structures with rough edges that scattered electrons, causing interference. The resulting nanoribbons had properties more like insulators than conductors.

“In our templated growth approach, we have essentially eliminated the edges that take away from the desirable properties of graphene,” de Heer explained. “The edges of the epitaxial graphene merge into the silicon carbide, producing properties that are really quite interesting.”

The “templated growth” technique begins with etching patterns into the silicon carbide surfaces on which epitaxial graphene is grown. The patterns serve as templates directing the growth of graphene structures, allowing the formation of nanoribbons and other structures of specific widths and shapes without the use of cutting techniques that produce the rough edges.

In creating these graphene nanostructures, de Heer and his research team first use conventional microelectronics techniques to etch tiny “steps” – or contours – into a silicon carbide wafer whose surface has been made extremely flat. They then heat the contoured wafer to approximately 1,500 degrees Celsius, which initiates melting that polishes any rough edges left by the etching process.

Established techniques are then used for growing graphene from silicon carbide by driving off the silicon atoms from the surface. Instead of producing a consistent layer of graphene across the entire surface of the wafer, however, the researchers limit the heating time so that graphene grows only on portions of the contours.

The width of the resulting nanoribbons is proportional to the depth of the contours, providing a mechanism for precisely controlling the nanoribbon structures. To form complex structures, multiple etching steps can be carried out to create complex templates.

“This technique allows us to avoid the complicated e-beam lithography steps that people have been using to create structures in epitaxial graphene,” de Heer noted. “We are seeing very good properties that show these structures can be used for real electronic applications.”

Since publication of the Nature Nanotechnology paper, de Heer’s team has been refining its technique. “We have taken this to an extreme – the cleanest and narrowest ribbons we can make,” he said. “We expect to be able to do everything we need with the size ribbons that we are able to make right now, though we probably could reduce the width to 10 nanometers or less.”

While the Georgia Tech team is continuing to develop high-frequency transistors – perhaps even at the terahertz range – its primary effort now focuses on developing quantum devices, de Heer said. Such devices were envisioned in the patents Georgia Tech holds on various epitaxial graphene processes.

“This means that the way we will be doing graphene electronics will be different,” he explained. “We will not be following the model of using standard field-effect transistors (FETs), but will pursue devices that use ballistic conductors and quantum interference. We are headed straight into using the electron wave effects in graphene.”

Taking advantage of the wave properties will allow electrons to be manipulated with techniques similar to those used by optical engineers. For instance, switching may be carried out using interference effects – separating beams of electrons and then recombining them in opposite phases to extinguish the signals.

Quantum devices would be smaller than conventional transistors and operate at lower power. Because of its ability to transport electrons with virtually no resistance, epitaxial graphene may be the ideal material for such devices, de Heer said.

“Using the quantum properties of electrons rather than the standard charged-particle properties means opening up new ways of looking at electronics,” he predicted. “This is probably the way that electronics will evolve, and it appears that graphene is the ideal material for making this transition.”

De Heer’s research team hopes to demonstrate a rudimentary switch operating on the quantum interference principle within a year.

Epitaxial graphene may be the basis for a new generation of high-performance devices that will take advantage of the material’s unique properties in applications where higher costs can be justified. Silicon, today’s electronic material of choice, will continue to be used in applications where high-performance is not required, de Heer said.

“This is an important step in the process,” he added. “There are going to be a lot of surprises as we move into these quantum devices and find out how they work. We have good reason to believe that this can be the basis for a new generation of transistors based on quantum interference.”

Permalink to this article

Northeastern University contracted for security using multiple sensor types including Terahertz

http://huntnewsnu.com/2011/03/nu-contracted-for-x-ray-security/
By Zack Sampson, News Staff
Backscatter X-ray units are used primarily in airports to provide high-quality images of passengers’ bodies, but the US Department of Homeland Security has joined with multiple research institutions, including Northeastern University, to test the use of such security technology in a mobile platform.
According to documents recently published by the Electronic Privacy Information Center (EPIC), Northeastern was contracted for $1,305,181 by the Department of Homeland Security to research the development of a transportable explosive sensor system in July 2006.
“Our idea is a mobile platform with a collection of sensors that work at different ranges … [to] try to get a sense of people who might have something suspicious beneath their clothing,” Carey Rappaport, a professor of computer and electrical engineering at Northeastern and principal investigator on the project, said.
Rappaport said the initiative is still going on in some forms, but will remain inactive until the Department of Homeland Security can allocate more funding for the studies.
Researchers worked on the “BomDetec Wide – Area Surveillance and Suicide Bomber Detection” program. It was a collaborative effort between multiple organizations including Raytheon, American Science & Engineering, Inc., Rensselaer Polytechnic Institute and the Siemens Foundation.
Rappaport said Northeastern was the “principal organizing entity” while the project was active. He said some students at the university were involved in algorithm-based work, and no experimentation with radar hardware occurred on-campus.
The BomDetec program centered on the development of an integrated system which could use data from four sensor types: intelligent video, radar, X-ray Backscatter and Terahertz radiation to detect and track potential suicide bombers at distances greater than 10 meters. Government defense institutions sought a final product that could serve foreign and domestic purposes.
The Department of Defense application of such a mobile unit would provide extra security at military checkpoints, Rappaport said.
“The idea was that it would be nice if you had a series of sensors that, in layers, could determine first of all if a person was suspicious, second of all if there might be something dangerous concealed under his clothing, third of all to confirm that there was something suspicious about this person,” he said.
Domestic security officials also planned to use the technology in a mobile form for scenarios such as a parade route passing by a reviewing stand.
“On the homeland side, wouldn’t it be great if you could park a van near the stand to make sure there wasn’t some idiot marching with these guys with a vest full of pipe bombs?” Rappaport said.
Theoretically, researchers hoped to place all sensors in a single hardwired van. Similar retrofitted vans already exist in more basic forms. American Science & Engineering, Inc. markets a Z Backscatter Van that has built-in X-ray equipment.
Rappaport said a van using all four sensors would need to be slightly larger, but still could be easily retrofitted.
“The X-ray was sort of the biggest thing, you could put video cameras on top of a van and nobody would even notice,” he said. “The radar fits into the size of maybe a telephone book … Terahertz is also about the size of a desktop computer.”
Rappaport said, for those moving in front of the Backscatter van, the system would work similar to security cameras at a mall.
“If you looked for it, you probably could find it,” he said. “But you really wouldn’t know about it unless you were looking for it. It’s not as secretive as traffic radar police use to catch speeders; that’s really hidden.”
Some, including members of EPIC, have expressed privacy concerns about mobile use of X-ray surveillance technology.
“This would allow them to take these technologies out of the airport and into other contexts like public streets, special events and ground transit. It’s a clear violation of the fourth amendment that’s very invasive, not necessarily effective and poses all the same radiation risks as the airport scans,” Ginger McCall, an attorney for EPIC, said in a recent Forbes Magazine article.
Rappaport said concerns of radiation risks are not significant.
“Taking pictures with video versus radar versus X-ray versus Terahertz, in no cases does any of it produce any sizable radiation that would have any health effects,” he said.
Rappaport added that the security vans would not necessarily produce the same images as an airport security system.
“[The images] probably wouldn’t be as high resolution as you’d get with an airport scanner because you are not standing right near it with your hands in the air,” he said.
Rappaport compared the actual images that Backscatter X-rays would produce in the mobile platform to looking at a person in a tight leotard or bathing suit like someone would wear at the beach.
“If that’s acceptable in some contexts, then it seems, in the interest of keeping everybody safe, it might be an acceptable compromise,” he said.
Rappaport emphasized that safety was his key motivator for the project.
“It’s satisfying to do this type of security research,” he said. “Everybody has thoughts of what is considered beneficial for society. But, all I have to do is have my device save the life of one nine-year-old girl … that makes a lot of the hard work seem worthwhile.”

Compact, high-power, room-temperature, narrow-line terahertz source

http://spie.org/x47313.xml?highlight=x2416&ArticleID=x47313

Jerome V. Moloney, Joe M. Yarborough, Mahmoud Fallahi, Maik Scheller, Stephan W. Koch and Martin Koch

A terahertz external-cavity surface-emitting-laser source delivering milliwatt powers at any targeted frequency across the tHz gap could address a broad range of applications.

15 March 2011, SPIE Newsroom. DOI: 10.1117/2.1201102.003523

Continuous-wave (CW) terahertz (THz) technology has long interested astronomers because approximately half of the total luminosity and 98% of the photons emitted since the Big Bang fall into the submillimeter (THz) and far-IR regimes. Submillimeter astronomy is the prime technique to unveil the birth and early evolution of a broad range of astrophysical objects. It is a relatively new branch of observational astrophysics that focuses on studies of the cold universe, i.e., objects radiating a significant (if not dominant) fraction of their energy at wavelengths from 100μm to 1mm. THz-continuum observations are particularly powerful to measure the luminosities, temperatures, and masses of cold, dusty objects. Examples of the latter include star-forming clouds in the Milky Way, prestellar cores and deeply embedded protostars, and protoplanetary disks around young stars, as well as nearby starburst galaxies and dust-enshrouded high-redshift galaxies in the early universe. In THz astronomy, high-power CW local oscillators (LOs) driving multipixel heterodyne receivers at key frequencies (e.g., at 1.4, 1.9, and 2.7THz) could be deployed on space-based and suborbital platforms.¹

THz waves have been notoriously difficult to generate and, consequently, this remains a relatively unexplored part of the electromagnetic spectrum. They also do not propagate far through the atmosphere, except in narrow transmission bands at selected frequencies. CW THz sources are highly desirable for a wide range of applications, from THz astronomy to spectroscopy, biosensing, and security and quality inspection in various industries, as well as for medical and pharmaceutical purposes. Many attempts have been made to fill the elusive THz gap (see Figure 1). On the low-frequency side, up to around 0.8THz, electronics-based sources have been successful, although their output power falls off rapidly with increasing frequency (see Figure 1). On the other side of the gap, fundamental physics limitations forces cryogenic operation of quantum-cascade-laser THz sources, since they have to overcome kT (∼26meV at room temperature, where k is Boltzmann's constant and T denotes temperature) to achieve population inversion. They typically emit poor beams (without addition of plasmonic-waveguide structures) with broad spectral lines, while performance drops off significantly below 3THz.

 

Figure 1. Terahertz (THz)-power performance of different sources around the THz gap. RTD: Resonant tunnel diode. IMPATT: Impact ionization avalanche transit-time diode. Gunn: Gunn laser. QCL: Quantum-cascade laser. III–V: Denotes groups III and V in the periodic table of elements. The yellow ellipse illustrates how the THz external-cavity surface-emitting-laser (TECSEL) source can span the gap.

Our THz external-cavity surface-emitting-laser (TECSEL) source, operating at room temperature, is based on intracavity difference-frequency generation using a periodically poled lithium niobate crystal.² Different nonlinear crystals can be employed in the cavity and designed for either collinear or noncollinear phase matching. The IR dual-wavelength, high circulating power is generated using an intracavity etalon placed in a high-finesse vertical-external-cavity surface-emitting laser (VECSEL) cavity. Dual-wavelength emission is facilitated by spectral-hole burning in the very broad gain of the host semiconductor medium, enabling generation of THz frequencies from 0.1 to 5THz and beyond. The choice of circulating IR wavelength is arbitrary, and the VECSEL chip can be designed either for IR, visible, or mid-IR emission to minimize intracavity losses and optimize THz extraction. Figure 2 shows the TECSEL cavity and breadboard setup for a noncollinear phase-matching geometry.

 

Figure 2. Illustration of the setup. The pump laser is directed by mirror M3 to the vertical-external-cavity surface-emitting laser (VECSEL)'s surface. The curved and flat mirrors M1 and M2, and the VECSEL chip, form the laser cavity. A Brewster window (BW) and an etalon are placed within the resonator to ensure generation of linearly polarized emission at two wavelengths. The two laser modes mix inside the nonlinear crystal (NLC) and generate THz radiation. THz waves are emitted from the crystal surface and collimated by a cylindrical THz lens. (b) Photograph of our setup. 1: Semiconductor VECSEL device. 2: Etalon. 3: BW. 4: M1. 5: NLC. 6: M2. 7: Cylindrical THz lens. 8: Head of the pump laser. 9: Circulating IR laser mode.

Our measured intrinsic linewidth is less than 1MHz, making it ideal as a local oscillator (LO) and/or spectroscopic source. We have already demonstrated that this source can generate milliwatt power levels at 0.825 (remote detection of explosives), 1, and 1.9THz (LO for an astronomical THz receiver). Figure 3 shows a direct comparison of the power output for the 1 and 1.9THz sources, showing quadratic power scaling with increasing pump power and frequency.

 

Figure 3. Measured THz output power as a function of the total intracavity power of both IR modes. f: Frequency.

For astronomical applications in particular, our TECSEL source could potentially serve as the LO to drive mixer arrays of ∼100 or more pixels, dramatically increasing the scientific return from suborbital and space-based observing platforms. Recent advances in device fabrication, micromachining, low-noise amplifiers, and digital-signal processing have significantly driven down the cost per pixel of heterodyne arrays. LO power currently determines the possible array size. The number of pixels a heterodyne receiver can have and, consequently, how much of the sky can be observed within a given period of time scales linearly with LO power. Therefore, continued development of VECSEL-based THz sources could significantly reduce required mission lifetimes and cost. We are currently collaborating with both the Steward Observatory Radio-frequency Laboratory (SORAL) at the University of Arizona and TeraVision LLC (Tucson, Arizona) to test our TECSEL source as both an LO at 1.9THz and a remote spectroscopic source for detection of explosives.³ Many common explosives have unique spectral signatures within the relatively inaccessible spectral window between 0.8 and 3THz. A CW narrow-line source can reveal high-resolution spectroscopic features that are not observable with time-domain THz spectroscopy.

In summary, our room-temperature TECSEL source delivers milliwatt-level powers with sub-MHz linewidth in a clean Gaussian beam at any targeted frequency within and outside the THz gap. Further development is needed to optimize the source, minimize thermal effects in the VECSEL chip and nonlinear crystal, and further scale the emitted THz power. For example, we know that at least 50% of the THz power emitted into the NLC is currently absorbed. Our patented technology covers a broad landscape of TECSEL configurations, including collinear difference-frequency generation in transparent NLCs. Moreover, the TECSEL can be operated in pulsed mode to generate extremely high peak THz powers for time-domain-spectroscopy applications.

Our TECSEL 1.9THz source development has been funded by NASA Phase 1 and 2 Small Business Innovation Research (SBIR) contracts to Desert Beam Technologies, while 0.825THz source development was funded by a National Science Foundation Phase 1 SBIR. The authors acknowledge discussions with and support from Christopher Walker of SORAL, and Christian d'Aubigny and Abraham Young of Teravision LLC (Tucson, Arizona).

---

Jerome V. Moloney, Joe M. Yarborough, Mahmoud Fallahi

Desert Beam Technologies LLC

Tucson, AZ 

Jerome Moloney is a professor of optical sciences and mathematics at the University of Arizona and a partner in Desert Beam Technologies LLC. His research interests include theory and experimental study of semiconductor lasers, ultrafast extreme nonlinear optics, and computational photonics.

Joe Yarborough is a senior scientist. His research includes tunable lasers, nonlinear optics, and THz sources.

Mahmoud Fallahi is a professor and a partner in Desert Beam Technologies LLC. His research interests are in semiconductor lasers, integrated optics, micro/nanofabrication, and polymer/hybrid components.

Maik Scheller, Stephan W. Koch, Martin Koch

Department of Physics
Philipps University Marburg

Marburg, Germany

Maik Scheller received his Dipl-Ing degree in electrical engineering from the Technical University of Braunschweig (Germany) in 2008. He is currently pursuing a PhD degree. His research interests include nonlinear optics, THz systems, and signal processing.

Stephan W. Koch has been a professor of physics at Philipps University Marburg and a research professor at the Optical Sciences Center of the University of Arizona since 1993. He is also a partner in Desert Beam Technologies LLC. His fields of major current interests include condensed-matter theory, optical and electronic properties of semiconductors, many-body interactions, disorder effects, quantum confinement in solids, coherent and ultrafast phenomena, semiconductor-laser theory, microcavity effects, and optical instabilities and nonlinearities.

Martin Koch is a professor of physics and a partner in Desert Beam Technologies LLC. His research interests include ultrafast spectroscopy of semiconductors, semiconductor physics, and THz-systems technology.

---

References:

1. P. Siegel, Terahertz technology, IEEE Trans. Microw. Theory Techn. 50, no. 3, pp. 910, 2002.

2. M. Scheller, J. M. Yarborough, J. V. Moloney, M. Fallahi, M. Koch, S. W. Koch, Room temperature continuous wave milliwatt terahertz source, Opt. Express 18, pp. 27112-27117, 2010.

3. J. F Federici, B. Schulkin, F. Huang, D. Gary, R. Barat, F. Oliveira, D. Zimdars, THz imaging and sensing for security applications: explosives, weapons and drugs,Semicond. Sci. Technol. 20, pp S266, 2005.

Newport Announces Terahertz Pulse Generation Kit

http://www.photonicsonline.com/article.mvc/Newport-Announces-Terahertz-Pulse-Generation-0001?atc~c=771+s=773+r=001+l=a

March 16, 2011

Newport Corporation, a worldwide leader in laser and photonic solutions, introduces the new terahertz (THz) pulse generation kit using a sub-35-fs Ti:sapphire amplifier system. The kit can be easily integrated with a Ti:sapphire amplifier to generate terahertz pulses which can be further used for linear, nonlinear, and time-resolved spectroscopy applications.

The THz pulse generation kit utilizes standard Newport optics, opto-mechanics, manual stages, and CONEX-based motorized solutions to provide high performance and accuracy. The 800 nm Ti:sapphire laser pulse (1 kHz, ~ 300 µJ per pulse) is focused into ambient air to generate the air plasma which produces THz pulses. With this innovative design, the damage threshold is not a concern as the air replenishes itself from pulse to pulse. The generated THz pulse has the oscillation that spans about 1 ps and has the estimated pulse energy of 0.1 - 0.3 nJ per pulse. Furthermore, the ability to recover the phase and the amplitude information of the THz field through electro-optic sampling enables the kit to function as aTHz spectrometer, without further modification.

Keshav Kumar, Product Marketing Manager, Optics & Technology and Applications Center (TAC) Products, Newport Corporation, notes, "Our new air plasma based THz pulse generation kit is a preconfigured and versatile solution for researchers. It integrates Newport's existing world class standard photonics components to provide higher performance and superior reliability. It can be easily integrated with amplifier-based laser systems to generate high energy Terahertz pulses for several demanding applications. These include characterization of nanomaterials, detecting security sensitive explosives, biomolecular spectroscopy, and telecommunication applications. We are proud to introduce this exciting, new easy-to-use and economical solution to the research community."

About Newport Corporation
Newport Corporation is a leading global supplier of advanced-technology products and systems to customers in the scientific research, microelectronics manufacturing, aerospace and defense/security, life and health sciences and precision industrial manufacturing markets. Newport's innovative solutions leverage its expertise in high-power semiconductor, solid-state and ultrafast lasers, photonics instrumentation, sub-micron positioning systems, vibration isolation, optical subsystems and precision automation to enhance the capabilities and productivity of its customers' manufacturing, engineering and research applications. Newport is part of the Standard & Poor's SmallCap 600 Index and the Russell Microcap Index. For more information, visit: http://www.newport.com/THz

SOURCE: Newport Corporation