**1. Introduction**

A low wavelength of the laser beam and a very short pulse (ns‐fs) duration induce instant local vaporizationonthesurfaceofatargetmaterialgeneratingaplasmaplumeconsistingofphotons, electrons, ions, atoms, molecules, clusters, and liquid or solid particles. This phenomenon is known in the literature as '**laser ablation'** [1], a term derived from the Latin word '*ablatio'*, meaning 'to carry away'.

Shortly, after the first laser functionality demonstration in 16 May 1960, numerous theoretical and experimental studies were performed concerning the interaction of the high intensity laser beam with solids [2–4], liquids [5], and gases [6].

Laser ablation is the base principle of most applications involving laser processing of materials: precise cutting, hole drilling, laser cleaning of surfaces, compositional analysis, and thin film deposition. The latter came as an obvious application, as a plate/slide/wafer can easily be positioned in front of the plasma plume, acting as a collector for the hot ablated material that condenses in the form of a thin film. This deposition method is known as pulsed laser deposition (PLD). The earliest attempt of thin film deposition was made in 1965 by Smith and Turner [7], but the true breakthrough was achieved by Dijjkamp et al. in 1987 [8], who succeeded the stoichiometric transfer of a compound with a complex molecular structure, very difficult to obtain using other deposition techniques. In this situation, it can be considered that a *congruent ablation* was attained. The decrease in the pulse duration meant laser beams with higher delivered energies that significantly increased the range of materials that could be ablated [9].

Historically, the method was known under several denominations [9]: pulsed laser evapora‐ tion, laser induced flash evaporation, laser molecular beam epitaxy, laser assisted deposition and annealing, and laser sputtering.

Some variations in PLD emerged out of necessity to deposit more complex materials or materials degradable at high temperatures. Instead of a single laser beam as in classical PLD, two laser beams can be used simultaneously to ablate two targets mounted on a carousel system, producing a mix of plasmas that will generate thin films with variable composition over the surface. This variation in PLD is known in the literature as combinatorial pulsed laser deposition (CPLD) [10].

Another variation in PLD developed out of necessity to protect compounds with long and fragile molecular chains is called matrix‐assisted pulsed laser evaporation (MAPLE), and it uses as the target, a frozen mix consisting of the active material to be deposited and a buffer matrix that preponderantly absorbs the laser beam energy [11].

All these variations in PLD will be discussed in detail in the next chapters with relevant ex‐ amples for their advantages and drawbacks.
