Extending filamentation

Femtosecond filamentation is an appealing self-organization phenomenon in optical physics that has been awaiting practical applications for a long time. First described some 20 years ago1, the collapse of the spatial beam profile of a femtosecond laser beam may lead to the formation of metre-long plasma channels in atmospheric air. These plasma channels resemble those generated by electric discharges but are absolutely straight, without any bends or turns. Despite the undisputed beauty of this phenomenon, femtosecond filamentation has led to only a limited number of applications to date (for example, pulse self-compression2). One critical issue hindering the development of many other attractive applications is the restricted length of single filaments. Writing in Nature Photonics, Maik Scheller and colleagues describe the use of dressing laser beams as a promising new approach for generating extended OPTICAL PHYSICS