High-harmonic generation (HHG) is a non-linear optical process that can convert laser light with standard wavelengths, such as infrared light, into coherent radiation at much shorter wavelengths in the XUV (extreme ultraviolet) or soft X-ray regime. As opposed to low-order nonlinear frequency conversion processes, such as second-harmonic generation, where moderate laser intensities are su cient, high-order harmonics result from the highly nonlinear interaction of high-intensity laser pulses with typically a gaseous medium . Ultrashort laser pulses of femtosecond duration are used for the generation of highharmonics, focused to very high intensities ( 1014 W/cm2) at a gaseous target. In the strong eld present at the laser focus, electrons are ionized from the gas atoms. These electrons gain additional energy in the laser eld and, upon recombination with the parent ion, emit harmonic XUV radiation. As the process of ionization and recombination takes place every half-cycle of the laser pulse, a spectrum of odd harmonics of the fundamental
laser frequency is generated.
|Place of Publication||Enschede|
|Number of pages||54|
|Publication status||Published - 27 Aug 2012|