chapter  6
44 Pages

Applications of Ultra-Short Laser–Matter Interactions

A number of distinctive features of ultra-short lasers interaction with mat-

ter have attracted several specific applications, which are described below.

First feature to be mentioned is the ability to control the phase state of ab-

lated vapours through the optimum pulse and focusing conditions adjusted

to the ablated material properties. This feature ensured the application of

ultra-short lasers for the ablation of different materials with the subsequent

condensation of ablated plume on a substrate for producing the thin films

of superb quality. The ablation of solids by powerful lasers of differ-

ent pulse duration has attracted a significant attention during the past

decades due to many potential applications of this effect in industry, medi-

cine, material science and technology. However, pulsed laser deposition

(PLD) when applied in its conventional form using low-repetition rate lasers

emitting nanosecond-range pulses [Chrisey and Hubler, 1994, Miller and

Haglund, 1998] generally leads to poor quality films contaminated by par-

ticles. It has been shown that this disadvantage of conventional PLD is

a direct consequence of the ablation regime due to the far from the op-

timum laser parameters [Gamaly et al., 1999; Rode et al., 1999]. The

plume produced in long-pulse regime expands as a super-saturated vapour

and therefore condensation occurs during the early stage of the expan-

sion resulting in the formation of droplets from the vapour phase, that

are then deposited onto the substrate. It has been shown in Chapter 4

that the ablated plume can be kept in atomised state during the expan-

sion stage through the proper choice of pulse duration, wavelength and

energy along with a proper spatial and temporal distribution of the laser

intensity during the pulse time and across the focal spot keeping the ab-

sorbed laser energy above some specific threshold. The experimental imple-

mentation of these recipes for deposition of different materials is presented

later in this section.