Toward a New Laser Induced Hydrodynamic Forward Transfer Process with Femtosecond Lasers

We describe self-consistently the relevant laser interaction with transparent dielectrics. A laser beam focused in the bulk with a laser energy of 100 nJ reaches intensities greater than 8 x 10(13) W/cm(2) due to the very small focusing area. An estimate of this focal area is given by S-foc = pi x R-w(2), with R-w the laser focal radius of typically 500 nm. The material experiences optical breakdown in the bulk, i.e. near the focal section, and is thus ionized, i.e. converted into a hot and dense plasma. The shock and rarefaction waves which are generated may produce a void inside the target as is it now classically understood from experimental and modeling (Gamaly et al. 2006 [1]). Typical dimensions of the obtained voids are submicrometric, i.e. 0.2 mu m(3) in the previously described laser configuration. In confined geometries we show that jets can develop. Jet's sizes and expansion velocities depend both on laser energy and distance from the rear surface. This jet formation regime, apparently new, can be related to some Laser Induced Forward Transfer (LIFT) process, with submicrometer jet diameters. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim