INSTITUTE OF APPLIED PHYSICS - Ultrafast source of attosecond light flashes for fundamental science

Ultrafast source of attosecond light flashes for fundamental science

Schematic representation of the generation of isolated attosecond pulses. A few-cycle laser pulse (red) interacts with argon atoms in a thin gas jet and generated a shorter wavelength pulse (blue) having a duration in the attosecond range.

Investigation and observation of ever smaller scales and faster processes requires the development of new measurement techniques. The observation of electrons in atoms and molecules is of particular importance, since they facilitate important chemical, biological and physical processes. Decoding of such processes allows a deeper understanding of fundamental physical theories such as quantum mechanics or atomic and molecular physics, but also promotes technological improvements.

To solve these issues, ultrashort laser pulses were used, which were focused on a noble gas and thereby generated X-ray flashes. If the duration of the incident laser pulse is reduced to a few optical oscillations, exactly one X-ray flash per laser pulse is emitted with a duration in the attosecond range. An attosecond is a billionth of a billionth of a second (10-18 s = 0.000000000000000001 s). To get an impression of this dimension, you can face the ratio of an attosecond to a second with the ratio of one second to the age of the universe. The flashes, called isolated attosecond pulses, can be used similarly to a stroboscope to make the extremely fast processes in atoms, molecules or surfaces visible.

However, due to the fact that conventionally used laser systems can only emit a few thousand pulses per second, the generation and application of these pulses is still very limited. But for the recording of multi-dimensional data, such as videos or coincidence measurements, a significantly higher repetition rate is required.

For the first time, a team of researchers from the Institute of Applied Physics Jena (University Jena), the Max-Born Institute in Berlin and the Imperial College London has now demonstrated the generation of isolated attosecond pulses at unprecedented repetition rates. They were able to demonstrate a 200-fold increase of this important parameter and pave the way for a vast variety of new applications in the young field of attosecond physics. To realize this important step the scientists developed a novel optical parametric amplifier that was pumped with a fiber laser. This has enabled a unique laser system to emit two cycle pulses with repetition rates as high as Megahertz. They focused the pulses onto a thin jet of argon atoms and were able to observe strong evidence of isolated attosecond pulse generation in the optical spectrum of the emitted ration, which was substantiated by quantum mechanical simulation of their experiments. The obtained results offer a new insight into atomic and molecular processes by enabling methods such as time-resolved photoelectron spectroscopy or even time-lapse recording of microscopic events in attosecond surface science.

Original publication:

Krebs, M. et al. Towards isolated attosecond pulses at megahertz repetition rates. Nature Photonics 7, 555-559 (2013). DOI:10.1038/nphoton.2013.131

Jun.-Prof. Dr. Jens Limpert
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News from: 19.06.2013 15:09
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