Experimental observation of second-harmonic generation and diffusion inside random media

We have experimentally measured the distribution of the second-harmonic intensity that is generated inside a highly-scattering slab of porous gallium phosphide. Two complementary techniques for determining the distribution are used. First, the spatial distribution of second-harmonic light intensity at the side of a cleaved slab has been recorded. Second, the total second-harmonic radiation at each side of the slab has been measured for several samples at various wavelengths. By combining these measurements with a diffusion model for second-harmonic generation that incorporates extrapolated boundary conditions, we present a consistent picture of the distribution of the second-harmonic intensity inside the slab. We find that the ratio $\ell_{2\omega}/L_c$ of the mean free path at the second-harmonic frequency to the coherence length, which was suggested by some earlier calculations, cannot describe the second-harmonic yield in our samples. For describing the total second-harmonic yield, our experiments show that the scattering parameter at the fundamental frequency \k_{1\omega}\ell_{1\omega} is the most relevant parameter in our type of samples.Comment: 10 pages, 7 figure

Picosecond time drift characterization of the Laser MegaJoule timing system

International audienc

Oscillateurs laser femtosecondes à base de cristaux de borates inédits dopés aux ions ytterbium

Nous présentons ici les résultats obtenus à l'aide de nouveaux cristaux de borates dopés aux ions ytterbium : Yb:GdCOB, Yb:BOYS. Ces cristaux ont été utilisés pour réaliser des oscillateurs laser produisant des impulsions inférieures à 100 fs vers 1050 nm, dont les modes sont verrouillés en phase à l'aide d'absorbant saturable à semi-conducteurs. Ces oscillateurs femtosecondes de nouvelle génération directement pompés par des diodes laser de puissance ont l'avantage d'être compacts, performants et très stables