Researchers at the U.S. Department of Energy's Brookhaven National Laboratory have generated extremely short pulses of light that are the strongest of their type ever produced and could prove invaluable in probing the ultra-fast motion of atoms and electrons. The scientists also made the first observations of a phenomenon called cross-phase modulation with this high-intensity light - a characteristic that could be used in numerous new light source technologies.
The work, which was done at Brookhaven's Source Development Laboratory, an offshoot of the Lab's National Synchrotron Light Source (NSLS), is described online in the July 23, 2007, edition of Physical Review Letters.
The light pulses used were in the terahertz (THz) range of the broad electromagnetic spectrum, found between the microwave and infrared range. Scientists send tight bunches of electrons at nearly the speed of light through a magnetic field to produce THz radiation at a trillion cycles per second - the terahertz frequency that gives the light its name and that makes them especially valuable for investigating biological molecules and imaging, ranging from tumor detection to homeland security.
The Brookhaven team is looking to expand the potential uses for this type of light by increasing the strength of individual THz pulses, a longtime goal for scientists in the field. By slamming an electron beam from an accelerator into an aluminum mirror, the researchers produced 100 microjoule (100 megawatt) single-cycle pulses - the highest energy ever achieved to date with THz radiation. For comparison, 100 megawatts is about the output of a utility company's electrical generator.
The combination of this newfound strength with ultra-fast pulses provides researchers with a powerful new tool to study the movement of a material's electrons (which zip around at the femtosecond, or quadrillionth of a second, timescale) or atoms (which move at the picosecond, or trillionth of a second, timescale).
"The goal is really to understand the properties of materials," said NSLS researcher Yuzhen Shen, the lead author of the paper. "One might ask what happens in a solid when light, electricity, or sound goes through it, and it's all related to atoms in a crystal wiggling around or the movement of electrons. So the effort surrounding ultra-fast pulses is going into making tools to probe the real fundamental properties of materials on the scales at which they move."
Using this strong light, researchers can "kick" molecular processes such as catalysis or electronic switching (important for developing data storage media) into action and watch their mechanisms on a very short timescale.
The team also found something surprising: the intensity of their THz pulses is so great that they introduce so-called "nonlinear optical effects," specifically, a phenomenon known as cross-phase modulation.
"When you pull on a spring, if you pull twice as hard, it stretches twice as much," said NSLS researcher Larry Carr. "But there's a limit where if you pull twice as hard, the spring doesn't move anymore. That's when it's called nonlinear. The same thing happens in materials. You let these short pulses pass through a material, and they stress it and pull some of the charges apart so they don't act in a linear manner."
As a result, the researchers can manipulate both the ultra-fast THz pulses and the material they interact with. Some of the simplest examples include changing the color of the light or turning the material into a focusing lens.
This is the first time cross-phase modulation has been observed in single-cycle THz pulses. Learning how to control this characteristic could lead to even more light source technologies.
This research was supported by the Office of Basic Energy Sciences within the U.S. Department of Energy's Office of Science, the Office of Naval Research, and Brookhaven's Laboratory Directed R&D funds.
Karen McNulty Walsh | EurekAlert!
APEX takes a glimpse into the heart of darkness
25.05.2018 | Max-Planck-Institut für Radioastronomie
First chip-scale broadband optical system that can sense molecules in the mid-IR
24.05.2018 | Columbia University School of Engineering and Applied Science
The more electronics steer, accelerate and brake cars, the more important it is to protect them against cyber-attacks. That is why 15 partners from industry and academia will work together over the next three years on new approaches to IT security in self-driving cars. The joint project goes by the name Security For Connected, Autonomous Cars (SecForCARs) and has funding of €7.2 million from the German Federal Ministry of Education and Research. Infineon is leading the project.
Vehicles already offer diverse communication interfaces and more and more automated functions, such as distance and lane-keeping assist systems. At the same...
A research team led by physicists at the Technical University of Munich (TUM) has developed molecular nanoswitches that can be toggled between two structurally different states using an applied voltage. They can serve as the basis for a pioneering class of devices that could replace silicon-based components with organic molecules.
The development of new electronic technologies drives the incessant reduction of functional component sizes. In the context of an international collaborative...
At the LASYS 2018, from June 5th to 7th, the Laser Zentrum Hannover e.V. (LZH) will be showcasing processes for the laser material processing of tomorrow in hall 4 at stand 4E75. With blown bomb shells the LZH will present first results of a research project on civil security.
At this year's LASYS, the LZH will exhibit light-based processes such as cutting, welding, ablation and structuring as well as additive manufacturing for...
There are videos on the internet that can make one marvel at technology. For example, a smartphone is casually bent around the arm or a thin-film display is rolled in all directions and with almost every diameter. From the user's point of view, this looks fantastic. From a professional point of view, however, the question arises: Is that already possible?
At Display Week 2018, scientists from the Fraunhofer Institute for Applied Polymer Research IAP will be demonstrating today’s technological possibilities and...
So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics
Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...
25.05.2018 | Event News
02.05.2018 | Event News
13.04.2018 | Event News
25.05.2018 | Event News
25.05.2018 | Machine Engineering
25.05.2018 | Life Sciences