Zenghu Chang breaks record for shortest laser pulse - again

08 Aug 2017

UCF demonstrates “fastest ever light pulse”, a 53-attosecond X-ray flash, beating its own 67-attosecond EUV burst, set in 2012.

A research team at the University of Central Florida has demonstrated what it calls “the fastest light pulse ever developed”, a 53-attosecond X-ray flash. The group led by Professor Zenghu Chang beat its own record set in 2012: a 67-attosecond extreme ultraviolet light pulse, which was the fastest at the time.

Attosecond light pulses allow scientists to capture images of fast-moving electrons in atoms and molecules with unprecedented sharpness. The work was reported in Nature Communications.

The pulses that Prof. Chang has now demonstrated are not just shorter in duration, but also in wavelength. The new light reaches an important spectral region, the so called “water window,” where carbon atoms absorb strongly but water does not.

Observing reaction mechanisms

“Such attosecond soft X-rays could be used to make a slow-motion video of electrons and atoms of biological molecules in living cells to, for instance, improve the efficiency of solar panels by better understanding how photosynthesis works,” said Prof. Chang, a UCF Trustee Chair Professor in CREOL, the College of Optics & Photonics, and the Department of Physics.

He is also the director of the Institute for the Frontiers of Attosecond Science and Technology, located in the Physics Department, where the experiments were carried out.

X-rays interact with the tightly-bound electrons in matter and may reveal which electrons move in which atoms, providing another way to study rapid processes in materials with chemical element specificity. That capability is invaluable for such developments as next-generation logic and memory chips for mobile phones and computers that are a thousand times faster than those in use today.

Producing attosecond X-rays requires a new type of high power driver: femtosecond lasers with a long wavelength. This is an approach that Prof. Chang and his team have pioneered.

Chang’s team includes Jie Li, Xiaoming Ren, Yanchun Yin, Andrew Chew, Yan Cheng, Eric Cunningham, Yang Wang, Shuyuan Hu and Yi Wu, who are all affiliated with iFAST; Kun Zhao, who is also affiliated with the Chinese Academy of Sciences; and Michael Chini with the UCF Department of Physics.

The research was supported by grants through the DARPA PULSE program, the US Army Research Office, and the US Air Force Office of Scientific Research, and is based on work supported by the US National Science Foundation.

Paper conclusion

The Nature Communications paper summarizes the achievement as follows: “Attosecond pulses at photon energies corresponding to the fundamental absorption edges of matter, which lie in the soft X-ray regime above 200eV, permit the probing of electronic excitation, chemical state, and atomic structure.

“Here we demonstrate a soft X-ray pulse duration of 53 attoseconds and single pulse streaking reaching the carbon K-absorption edge (284 eV) by utilizing intense two-cycle driving pulses near the 1.8µm center wavelength. Such pulses permit studies of electron dynamics in live biological samples and next generation electronic materials such as diamond.”