Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Light oscillations become visible

30.08.2004


Austrian-German research team demonstrates for the first time an attosecond "oscilloscope" rendering the hyper-fast field oscillations of visible light


Fig. 1: Energy shift (in units of eV) suffered by an attosecond electron probe set free at different instants (measured in units of fs) in an intense wave consisting of only a few cycles of red light. Image: Max Planck Institute for Quantum Optics / Technical University Vienna


Fig. 2: Build-up and disappearance of the electric field in the 4.3-fs pulse of red light (wavelength ~ 750nm), as recorded by the attosecond oscilloscope. Image: Max Planck Institute for Quantum Optics / Technical University Vienna



The human eye can detect changes in the intensity of light, not however the wavelength because light oscillates too fast (approximately 1000 trillion times per second). An international collaboration led by Ferenc Krausz and made up of researchers from the Vienna University of Technology, the Max-Planck-Institute for Quantum Optics and the University of Bielefeld have recently succeeded in developing a technique which can measure the instantaneous electric field of red light (quarter period ~ 620 attoseconds) and record its variation with a resolution of 100 attoseconds (Science, August 27, 2004). The experiment of the Austrian-German team allowed the first direct visualization of the electric field of visible light and constitutes the fastest measurement to date.

It has been known since the famous experiments of Heinrich Hertz near the end of the 19th century that light is a wave consisting of electric and magnetic fields, just as radio waves and microwaves. The only difference is in the number of times these fields change their direction in a second. In radio and microwaves this happens typically millions to trillions times per second. The field variation in these waves can be readily detected by turning it into electric current and displaying the variation of this current in electronic instruments called oscilloscopes.


In striking contrast, the electromagnetic field of visible light changes direction approx. one thousand trillion, i.e. 1 000 000 000 000 000, times per second, so that the instantaneous intensity of the light field varies from zero to maximum faster than a femtosecond (1 femtosecond being one thousandth of a trillionth of a second), some ten thousand times more rapidly than the resolution of the fastest electronic instruments available to date. Recording the field variation of visible light calls for an oscilloscope that exhibits a temporal resolution of several hundred attoseconds (1 attosecond being a thousandth of a femtosecond). The researchers recently succeeded in developing a technique which can measure the instantaneous electric field of red light (quarter period ~ 620 attoseconds) and record its variation with a resolution of 100 attoseconds.

The key to this measurement was the generation of single 250-attosecond extreme ultraviolet pulses, a feat achieved by the same collaboration a few months ago (Nature, February 26, 2004). The attosecond extreme ultraviolet pulse knocks electrons free from atoms to probe the electric field of a wave consisting of only a few cycles of red laser light. The electric field of red light accelerated or decelerated the electrons set free with respect to the light wave with a 100-attosecond timing precision. The change in the electrons’ energy (shown in units of electron volts, eV, in Fig. 1), measured as a function of delay (shown in units of femtoseconds, fs, in Fig. 1) between the attosecond pulse and the laser light wave clearly exhibits the build-up and disappearance of the laser pulse within a few femtoseconds as well as oscillations with a period of the 2.5-fs wave cycle of 750-nm (red) light. The measured energy change directly yields the variation of the instantaneous strength and direction of the electric field of the few-cycle light wave (Fig. 2).

The red line in Fig. 2 depicts the electric field of a few-femtosecond flash of red light, as recorded by an apparatus that can be regarded as the first attosecond oscilloscope. The new technique permits direct and accurate measurement of ultrabroad-band light pulses (made up of many different colours), and thereby opens the door to the reproducible synthesis of ultrashort flashes of light with arbitrary waveform for a number of applications including the development of molecular electronics and X-ray lasers.

Dr. Bernd Wirsing | EurekAlert!
Further information:
http://www.mpg.de

More articles from Power and Electrical Engineering:

nachricht New creepy, crawly search and rescue robot developed at Ben-Gurion U
19.07.2018 | American Associates, Ben-Gurion University of the Negev

nachricht The role of Sodium for the Enhancement of Solar Cells
17.07.2018 | Max-Planck-Institut für Eisenforschung GmbH

All articles from Power and Electrical Engineering >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

Im Focus: Chemical reactions in the light of ultrashort X-ray pulses from free-electron lasers

Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.

Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

Global study of world's beaches shows threat to protected areas

19.07.2018 | Earth Sciences

New creepy, crawly search and rescue robot developed at Ben-Gurion U

19.07.2018 | Power and Electrical Engineering

Metal too 'gummy' to cut? Draw on it with a Sharpie or glue stick, science says

19.07.2018 | Materials Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>