Air Photonics

Modern ultrashort laser sources routinely produce powerful enough pulses to ionize the ambient air, so that the very atmosphere we breath becomes an interesting medium for nonlinear photonics. One of the first and most prominent ultrafast nonlinear effects studied in air is filamentation [1], [2], and so-called femtosecond filaments have enabled many applications, for example remote supercontinuum generation [3] or pulse compression [4], [5], for review see [6], [7]. Air lasing [8] offering exciting possibilities for standoff detection [9] has been demonstrated. Moreover, air is easily exploited as nonlinear medium in hollow-core photonic crystal fibers [10].