Monday, April 25, 2016

Attosecond Physics May Make It Possible To Capture Even Electrons In Motion

By Debasmita Banerjee

The MIT media lab has already captured the imagination of the world with its magical Femtosecond photography technology. Upgrading the previous technology, a group of researchers from the Ludwig-Maximilians-Universität München have cumulated resources and prepared the initial steps needed to unleash the quickest photography technology ever, using Attosecond physics. The latest press release regarding the same, confirms that with some important modifications, the ultrashort electron pulse generator and controller will be upgraded to a moving electron tracker. 

The developed process relies on terahertz radiation and when finished, it will manage to answer important questions corresponding to solid state physics. Ultrashort electrons will image the interaction between electrons inside a closed space or outside due to external stimuli, which would shed light on properties like high-temperature superconductivity experienced in solid-state devices. When an electron scatters off a crystal, owing to quantum mechanical wave-like properties, they interact to create diffraction patterns. If the motion paths could be tracked and recorded, scientists could confirm the internal structure of the material with respect to a tinier and more precise scales than an atom. 

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Electron pulses (green, coming from the left) influence a micro-sized antenna, powered by laser-generated terahertz radiation (red) ​

Team leaders Dr. Peter Baum and Prof. Ferenc Krausz from the Laboratory for Attosecond Physics (LAP), LMU and the Max-Planck Institute of Quantum Optics (MPQ) along with their colleagues have proposed a revolutionary method to generate ultrashort electron pulses which are commonly produced with extreme difficulty due to its sluggish movement when compared to that of light. Instead of microwave technology, they decided to opt for optically fabricated terahertz radiation. The unique solution results in lengthwise downscaled electron pulses with the new possibility of filming electrons instead of just atoms.

Highlighting machinery complicacies, scientists made an apt choice by zeroing in on the electron as it possesses a 100,000 times shorter wavelength than the photon, but it has both rest mass and charge which makes it difficult to generate pulses. As an aid, scientists optimally used terahertz electromagnetic radiation (wavelength lying between microwave and infrared) and help the pulsed terahertz radiation to interact with electrons over a special antenna, which orients the latecomer electrons with higher speed than the earlier ones. After that, the compressed pulse covers a minimum duration to scatter off the material under investigation. 

Scientists could also calculate the length of the electron pulses at the desired position and it causes a second interaction between terahertz radiation with electrons, but with a different orientation so that a sidewise deflection is imposed on the electrons. Conclusively, the group has also designed virtual terahertz-stopwatch to monitor electron pulses. The research will also be applicable to study the interaction of light and matter in electron clouds. The research was exclusively published in the journal Science.

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