Ultrafast laser filamentation
Contact: Prof. Weiwei Liu
Ultrafast laser filamentation is a unique nonlinear optical phenomenon, during which ultrashort laser pulse could propagate over long distance with high intensity, overcoming nature diffraction and dispersion. Since the laser intensity is high enough, the optical medium will be ionized and a long plasma channel will be left behind the laser pulse. This plasma channel is often referred to as a filament. In condensed matters, the length and the diameter of the filament are about several millimeters and a few micrometers, respectively. While in gas media, such as air, the length of the filament may reach hundreds of meters and the diameter is in the scale of a hundred micrometer. The suggested application of the filamentation ranges from lightening control, to remote sensing, to pulse compression, to weather control and THz generation, etc.
During the filamentation, plenty optical processes are involved, including dispersion, diffraction, self-focusing, ionization, Raman excitation, self-phase modulation, four wave mixing, Cherenkov radiation, etc. On the other hand, the scales of the space and time are widely spanned in the study of filamentation. For example, in time, the shortest laser pulse duration may reach sub-cycle, while the life time of the plasma channel could extend up to many microseconds. The studied electromagnetic wave frequency also covers broad range of from UV, to visible, to IR and to THz. Furthermore, the filamentation can be observed in extensive transparent optical media such as liquids, glasses and gases. Since its application in atmosphere is particularly attractively, the dynamics of the interactions of ultrafast laser with aerosol, dust and turbulence are also important issues in the course of filamentation. All these concerns complicate the research about the filamentation, making it a challenge at the forefront of ultrafast laser science.
The main research interests in this field ranges from the fundamental nonlinear dynamics of filamentation, to its application in remote sensing and ultra-broadband intense THz pulse generation.
Refs：Science, 301, 61 (2003)；Nat. Phys., 2, 327 (2006)；Science, 324, 229 (2009)；Nat. Photon., 4, 451 (2010)；Nat. Photon., 4, 627, (2010)；PNAS,108, 3130 (2010)；Science, 331, 442 (2011)；PNAS,109, 15185 (2012)；Nat. Photon., 11, 16 (2017)