Physical Aspects of Ultra-Fast UV Laser Transfer

Abstract

Precise patterns with high density and sub-µm spatial resolution are fabricated by Laser-induced Forward Transfer (LIFT). By using ultra-fast UV laser pulses, the thermal e ects are minimal, the material transfer is highly directional and there is practically no damage to the transferred material. This is a non-contact, rapid and simple method applicable to a wide variety of target materials.

The physical aspects of the ultrafast UV laser transfer process are discussed while time-resolved stroboscopic Schlieren imaging is used to visualize and study the e ect of ultra-short (0.5 ps) and short (15 ns) pulses on the laser transfer process. In contrast to the ns laser, the directionality of the ejected material is very high in case of the sub-ps laser process. The shock wave propagation is expected to be the main mechanism for material removal in the sub-ps laser transfer process.

The use of sub-ps UV laser pulses ensures that, through linear and non-linear absorption regimes, a very thin layer of the target material absorbs the laser pulse energy initiating a thermo-elastic shock-assisted process that expels the remaining target material, which retains its functionality for further use in micro-printing applications.