**1. Introduction**

Different laser pulse regimes (nanosecond, picosecond and femtosecond) were used not only to generate nanoparticles but also to manipulate them. Different laser wavelengths were selected to reduce the size of the nanoparticles and change their morphology. The study in this filed focuses on using different laser types and parameters to generate and manipulate of micro- and nanomaterials. Researchers have used different types of lasers not only to produce new materials

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but also for precise micro- and nanomachining. Generating lasers with short and ultra-short pulse duration leads to high-precision laser processing. Lasers with pulse durations in the femtosecondtopicosecondrangedemonstrateasignificantdevelopmentinqualityfordifferent materials in comparison with nanosecond or longer laser pulses [1]. In addition, using pulsed lasers to produce nanoparticles in liquid environments is a promising alternative to chemical methods for the production of totally ligand-free colloidal nanoparticles [2].

In general, for laser material processing, two different laser pulse duration regimes are used: long pulse duration, such as nanosecond pulse duration, which generates quite a significant heat-affected zone in the material because "the pulse duration is longer than the thermalisation time of most metals" [3]. This type of laser is suitable for removing materials or ablation. Short pulse duration (picosecond laser) and ultra-short pulse duration (femtosecond laser) yield better results, suited to the production of high-precision micro- and nanomachining. Typical laser pulse durations for precise laser material processing are 10 ps or less. It has been shown that suitable laser pulse durations for the micromachining of copper and stainless steel are in the range of 10–100 ps [3].

However, there is little evidence that researchers have approached the issue of lasers in nanotechnology in terms of precise and controllable ablation and their ability to generate nanoparticles from different materials. Consequently, the aim of this chapter is to provide an overview of how different laser pulses can be used in laser-material interaction and the production of nanoparticles.

Two important parameters used to describe lasers are their pulse duration (width) and pulse repetition rate (PRR). As shown in **Figure 1a**, laser pulse duration can also be described as fullwidth at half of the maximum (FWHM) amplitude of the laser pulse. Pulse repetition rate or pulse repetition frequency refers to the number of pulses emitted per second. For 1 kHz of PRR, the time period *T* would be 0.001 s (see **Figure 1b**).

**Figure 1.** Pulse width or pulse duration (a) and pulse repetition rate (b) of a laser.

Two further parameters of pulsed lasers, which are especially relevant for ultrafast lasers, are the laser's peak power (Ppeak), which is equal to the laser pulse energy divided by laser pulse duration (Ppeak = Ep/τ) and the average laser power, which is equivalent to the laser pulse energy multiplied by the pulse repetition rate (Pave. = Ep×PRR) [4].

In this chapter, the author shows the effects of different laser pulse interactions (nanosecond, picosecond and femtosecond lasers) with materials and the ablation of nanoparticles in a liquid environment in terms of their size, size distribution, morphology and production rate (pro‐ ductivity).
