High-order laser harmonics (HHs) produced by the interaction between a very intense ultrashort laser pulse and a gas jet represent an extreme-ultraviolet (XUV) radiation source with high brightness, coherence and peak intensity. The characterization of processes involving the use of HHs deserves a particular attention in the design of the beamline that is demanded to manage the XUV radiation. From the instrumental point of view, the photon throughput depends mainly from the efficiency of the optical elements. Here we present the experimental study of the optical properties of thin carbon films to be used as grazing-incidence coatings for XUV HHs. Several carbon samples were deposited on plane glass substrates by electron beam evaporation technique. The sample reflectivity was measured at different incidence angles in the 6.7-120 nm (190-10 eV) region. The optical constants (real and imaginary part of the refraction index) have been calculated. The results are in good agreement with what is reported in the literature and confirm that carboncoated optics operated at grazing incidence have a remarkable gain over conventional metallic coatings in the XUV. Since XUV HHs co-propagate with the intense infrared laser generating beam, it is important to measure the damage threshold of the coating when exposed to ultrashort infrared laser pulses. The experimental results obtained on carbon samples will be presented.
Optical properties of carbon coatings for extreme-ultraviolet high-order laser harmonics
F Frassetto;L Poletto;M Negro;C Vozzi
2010
Abstract
High-order laser harmonics (HHs) produced by the interaction between a very intense ultrashort laser pulse and a gas jet represent an extreme-ultraviolet (XUV) radiation source with high brightness, coherence and peak intensity. The characterization of processes involving the use of HHs deserves a particular attention in the design of the beamline that is demanded to manage the XUV radiation. From the instrumental point of view, the photon throughput depends mainly from the efficiency of the optical elements. Here we present the experimental study of the optical properties of thin carbon films to be used as grazing-incidence coatings for XUV HHs. Several carbon samples were deposited on plane glass substrates by electron beam evaporation technique. The sample reflectivity was measured at different incidence angles in the 6.7-120 nm (190-10 eV) region. The optical constants (real and imaginary part of the refraction index) have been calculated. The results are in good agreement with what is reported in the literature and confirm that carboncoated optics operated at grazing incidence have a remarkable gain over conventional metallic coatings in the XUV. Since XUV HHs co-propagate with the intense infrared laser generating beam, it is important to measure the damage threshold of the coating when exposed to ultrashort infrared laser pulses. The experimental results obtained on carbon samples will be presented.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
