For more than 30 years, scientists conducted a harness the power of the terahertz radiation. Tucked between Infrared radiation and microwaves on the electromagnetic spectrum, terahertz radiation can penetrate clothing, plastics, and human tissue, but they are thought to be safer than x-rays. As they are incorporated in various levels of different molecules, they can be told except chemicals: terahertz scanner at airport checkpoint, such as possible, to determine whether a closed vial in a suitcase that aspirin, methamphetamine, or explosive.
But practical ways to generate terahertz radiation may be difficult to obtain. Traditional Gas Lasers operating in the correct frequency band, but they are large, expensive and power-hungry. A semiconductor Lasers - the kind you get in DVD player - small and free, but they are difficult to drive on a limited range of spectrum: to determine how long it took for the Infrared Lasers of the first CD players to the Blue Lasers on Blu-Ray discs.
In 1994 researchers at Bell Labs invented a new kind of small but powerful semiconductor laser called the quantum Cascade laser, and in 2002 was shown to operate at terahertz frequencies. However, no accurate assessment of the chemical composition of object exposure on continuous range of frequencies, which is incorporated in various stages.
In a paper appearing in the latest issue of Nature Photonics, HU Qing, a professor of electrical engineering at MIT's Research Laboratory of Electronics, and his colleagues describe the first practical method for matching terahertz satis Cascade Lasers. What is more, the method is fundamentally new approach to the laser could affect other technologies are emerging.
"From the beginning of the terahertz development in the 1970s, people try to [high power] is compact and adjustable sources, and until now, this is in fact, the first example of such a source," said Peter Siegel, a result of Submillimeter Wave Advanced Technology Group at NASA's Jet Propulsion Laboratory at Caltech. "Even Qing suggested much of the work he put in and the new ideas he pioneered and through pressure, despite numerous setbacks and competition from other groups. It really, in the end, came through with great ones."
Tuning with ordinary semiconductor laser usually requires the entire change-cavity light emitting, from time to time, if it does not require laser wide frequency range, a heating or cooling center will work. Hu compare the two approaches to change the string at the park on the button - all change - or iron them on a peg - voltage change. But it works very well with terahertz satis Cascade Lasers.
The third route to the park in a series transition to a diameter of: the lower pitched strings on a guitar change thicker than those higher pitched. And the technique is hu's, talk about, amending the diameter of the beam.
A ray of light can travel through space is considered as a wave, undulating up and down indefinitely until it is a physical object. But when the same beam is limited - in, say, or demonstrations of optical fiber, long thin, laser Cascade satis - the electromagnetic field mode pattern known as "horizontal." The transverse method is really only new wave perpendicular to the first, except that it dies out very quickly - to reduce undulations quickly - if it is further from the beam. Indeed, the waves die quickly so that it can be considered as simply a big wave perpendicular to the beam, but focused on.
Need a new hu is the technique for a certain type of laser with Cascade quantum wire laser, where the transverse mode of Wavelength - the width of one large wave - actually more than the width of the laser itself. Deforms other one block transfer near enough to the material the laser transverse mode, which changes after the Wavelength of the emitted light. In experiments, HU and his colleagues found that the metal block the shorter Wavelength of light, and silicon block is extended. The close of the various blocks also varies on the amount transferred.
Terahertz Cascade Lasers are satis one major disadvantage: they must be cooled with liquid nitrogen to very low temperatures. But Jerome Faist said the Swiss Federal Institute of Technology in Zurich, one of the inventors of the laser quantum Cascade, although room-temperature version with a difficult and long-term project, tell "us anything is possible." Siegel and offers that make the technique on hu's, "I can not see why the temperature of the laser was applied that would matter."
Hu gives a technology that can be applied as well as a new type of small laser can be used to fine-scale detection. Usually, no visible light Lasers can not be narrower than the Wavelength of light used, but researchers find ways to limit the fundamental using the Plasmon called virtual particles, as a wave through the cloud of electrons. A number of new forms of Plasmon Lasers also be adapted by manipulating the transverse mode.
In experiments, using the group hu's a mechanical lever to block or metal silicon laser near Cascade satis make one direction. But they design and build electronic chips that would benefit under the rule of micro-electromechanical devices to the silicon and metal blocks in different directions to give the exact range of laser and then going to make a long short wavelengths.
But practical ways to generate terahertz radiation may be difficult to obtain. Traditional Gas Lasers operating in the correct frequency band, but they are large, expensive and power-hungry. A semiconductor Lasers - the kind you get in DVD player - small and free, but they are difficult to drive on a limited range of spectrum: to determine how long it took for the Infrared Lasers of the first CD players to the Blue Lasers on Blu-Ray discs.
In 1994 researchers at Bell Labs invented a new kind of small but powerful semiconductor laser called the quantum Cascade laser, and in 2002 was shown to operate at terahertz frequencies. However, no accurate assessment of the chemical composition of object exposure on continuous range of frequencies, which is incorporated in various stages.
In a paper appearing in the latest issue of Nature Photonics, HU Qing, a professor of electrical engineering at MIT's Research Laboratory of Electronics, and his colleagues describe the first practical method for matching terahertz satis Cascade Lasers. What is more, the method is fundamentally new approach to the laser could affect other technologies are emerging.
"From the beginning of the terahertz development in the 1970s, people try to [high power] is compact and adjustable sources, and until now, this is in fact, the first example of such a source," said Peter Siegel, a result of Submillimeter Wave Advanced Technology Group at NASA's Jet Propulsion Laboratory at Caltech. "Even Qing suggested much of the work he put in and the new ideas he pioneered and through pressure, despite numerous setbacks and competition from other groups. It really, in the end, came through with great ones."
Tuning with ordinary semiconductor laser usually requires the entire change-cavity light emitting, from time to time, if it does not require laser wide frequency range, a heating or cooling center will work. Hu compare the two approaches to change the string at the park on the button - all change - or iron them on a peg - voltage change. But it works very well with terahertz satis Cascade Lasers.
The third route to the park in a series transition to a diameter of: the lower pitched strings on a guitar change thicker than those higher pitched. And the technique is hu's, talk about, amending the diameter of the beam.
A ray of light can travel through space is considered as a wave, undulating up and down indefinitely until it is a physical object. But when the same beam is limited - in, say, or demonstrations of optical fiber, long thin, laser Cascade satis - the electromagnetic field mode pattern known as "horizontal." The transverse method is really only new wave perpendicular to the first, except that it dies out very quickly - to reduce undulations quickly - if it is further from the beam. Indeed, the waves die quickly so that it can be considered as simply a big wave perpendicular to the beam, but focused on.
Need a new hu is the technique for a certain type of laser with Cascade quantum wire laser, where the transverse mode of Wavelength - the width of one large wave - actually more than the width of the laser itself. Deforms other one block transfer near enough to the material the laser transverse mode, which changes after the Wavelength of the emitted light. In experiments, HU and his colleagues found that the metal block the shorter Wavelength of light, and silicon block is extended. The close of the various blocks also varies on the amount transferred.
Terahertz Cascade Lasers are satis one major disadvantage: they must be cooled with liquid nitrogen to very low temperatures. But Jerome Faist said the Swiss Federal Institute of Technology in Zurich, one of the inventors of the laser quantum Cascade, although room-temperature version with a difficult and long-term project, tell "us anything is possible." Siegel and offers that make the technique on hu's, "I can not see why the temperature of the laser was applied that would matter."
Hu gives a technology that can be applied as well as a new type of small laser can be used to fine-scale detection. Usually, no visible light Lasers can not be narrower than the Wavelength of light used, but researchers find ways to limit the fundamental using the Plasmon called virtual particles, as a wave through the cloud of electrons. A number of new forms of Plasmon Lasers also be adapted by manipulating the transverse mode.
In experiments, using the group hu's a mechanical lever to block or metal silicon laser near Cascade satis make one direction. But they design and build electronic chips that would benefit under the rule of micro-electromechanical devices to the silicon and metal blocks in different directions to give the exact range of laser and then going to make a long short wavelengths.
