Generation of high harmonics in laser plasmas

The generation of high harmonics in laser–plasma interactions on the steep density gradients is discussed, especially by using short-pulse UV laser radiation. Low intensity experiments with 5·1015 W/cm2 generate harmonics in the VUV range, and the efficiency can be optimized by modifying the density gradient. To obtain higher harmonics and to clear some disagreements among different results concerning polarization properties of harmonics we switched for higher intensities. Our experimental arrangement makes it possible to obtain a 5·1017 W/cm2 intensity with a prepulse as low as 107 W/cm2 using a table-top system. Preliminary results and future trends for high-harmonics generation with this method are given.