44
Remanufacturing and Advanced Machining
applications, and lithography, and the rest is divided between displays, optical storage, and printing devices. Dimensional span of laser devices is impressive, too.
The smallest laser consists of 44-nm-diameter nanoparticles with a gold core and
dye-doped silica shell, with outcoupling of surface plasmon oscillations to photonic
modes at a wavelength of 531 nm (Noginov et al., 2009), while the largest occupies a
building with a footprint covering an area equivalent to just over three football fields
(Spaeth et al., 2016). The most powerful laser beam has been recently launched at
Osaka University in Japan, able to produce a beam with a peak power of 2,000 trillion watts (2 petawatts) for an incredibly short duration, approximately a trillionth of
a second or one picosecond (Sarri, 2015).
The unique characteristics of laser light make lasers very special devices. These
are (Hitz et al., 2001):
1. The capability to produce a narrow beam that can increase its energy intensity so that it is able to cut or weld metal or create tiny and wonderfully
precise patterns in a laser printer
2. High spectral purity
3. The way its waves are aligned
Laser processing of materials, both metals and nonmetals, such as cutting, drilling,
welding, heat treatment, etc., has several advantages over conventional techniques.
Laser drilling can be more quick and less expensive than the mechanical process.
There is no tool wear and lasers make cuts with a better edge quality than most
mechanical cutters, so that edges of cut metal parts rarely need to be filed or polished. Laser welding can often be more precise and less expensive than conventional
methods and is more compatible with robotics. Laser heat treatment involves heating
a metal part with laser light, increasing its temperature to a point where its crystal structure changes, causing surface hardening or enhanced wear resistance (Hitz
et al., 2001). In the case of new materials like metal foams, laser processing such as
laser forming, laser welding, laser cutting, and laser additive manufacturing can be
applied successfully (Changdar and Chakraborty, 2021).
1.10.1 classificaTion of lasers
According to their active medium, lasers can be categorized as solid-state, liquid,
or gas lasers (Powell, 2003). The solid-state laser principle is shown in Figure 1.12.
It is also possible to distinguish five groups: solid-state, semiconductor, liquid,
gas, and plasma lasers, as proposed by Šulc and Jelínková (2013). The authors admit,
however, that the solid-state and semiconductor lasers can be integrated into one
group, because both these active media are solids. In a narrower sense of the term,
solid-state lasers are systems whose active medium consists of a transparent solid
matrix, e.g., crystal, glass, or ceramics, doped by an optically active ion and using
optical pumping for excitation.
Yan and Takayama (2020) emphasize that solid-state lasers often use an active
species held in an insulating dielectric crystal, glass, or semiconductor material,
Remanufacturing and Advanced Machining
applications, and lithography, and the rest is divided between displays, optical storage, and printing devices. Dimensional span of laser devices is impressive, too.
The smallest laser consists of 44-nm-diameter nanoparticles with a gold core and
dye-doped silica shell, with outcoupling of surface plasmon oscillations to photonic
modes at a wavelength of 531 nm (Noginov et al., 2009), while the largest occupies a
building with a footprint covering an area equivalent to just over three football fields
(Spaeth et al., 2016). The most powerful laser beam has been recently launched at
Osaka University in Japan, able to produce a beam with a peak power of 2,000 trillion watts (2 petawatts) for an incredibly short duration, approximately a trillionth of
a second or one picosecond (Sarri, 2015).
The unique characteristics of laser light make lasers very special devices. These
are (Hitz et al., 2001):
1. The capability to produce a narrow beam that can increase its energy intensity so that it is able to cut or weld metal or create tiny and wonderfully
precise patterns in a laser printer
2. High spectral purity
3. The way its waves are aligned
Laser processing of materials, both metals and nonmetals, such as cutting, drilling,
welding, heat treatment, etc., has several advantages over conventional techniques.
Laser drilling can be more quick and less expensive than the mechanical process.
There is no tool wear and lasers make cuts with a better edge quality than most
mechanical cutters, so that edges of cut metal parts rarely need to be filed or polished. Laser welding can often be more precise and less expensive than conventional
methods and is more compatible with robotics. Laser heat treatment involves heating
a metal part with laser light, increasing its temperature to a point where its crystal structure changes, causing surface hardening or enhanced wear resistance (Hitz
et al., 2001). In the case of new materials like metal foams, laser processing such as
laser forming, laser welding, laser cutting, and laser additive manufacturing can be
applied successfully (Changdar and Chakraborty, 2021).
1.10.1 classificaTion of lasers
According to their active medium, lasers can be categorized as solid-state, liquid,
or gas lasers (Powell, 2003). The solid-state laser principle is shown in Figure 1.12.
It is also possible to distinguish five groups: solid-state, semiconductor, liquid,
gas, and plasma lasers, as proposed by Šulc and Jelínková (2013). The authors admit,
however, that the solid-state and semiconductor lasers can be integrated into one
group, because both these active media are solids. In a narrower sense of the term,
solid-state lasers are systems whose active medium consists of a transparent solid
matrix, e.g., crystal, glass, or ceramics, doped by an optically active ion and using
optical pumping for excitation.
Yan and Takayama (2020) emphasize that solid-state lasers often use an active
species held in an insulating dielectric crystal, glass, or semiconductor material,