Chapter

Laser Machining
Natarajan Jeyaprakash, Che-Hua Yang
and Manickam Bhuvanesh Kumar

Abstract

The increasing demands of materials with superior properties are given priority
by most of the industries in recent years due to their higher performance levels.
Machining of hard materials is a challenging task since it involves higher cutting
forces and rapid tool wear. This leads to complexity in shaping these difficult-to
machine materials such as advanced composite and ceramics. There have been many
alternative techniques developed to overcome the shortcomings of conventional
machining processes. Laser beam machining (LBM) is one of the advanced non-
contact machining processes that employ monochromatic light with high frequency
for machining using thermal energy. The highly energized photos are focused on a
material cause heating, melting and vaporizes the material which is effectively used
to remove unwanted portion of a material. Due to higher coherency of laser beam,
materials can be machined very precisely than conventional machining processes.
Generally, the laser-based material processing is suitable for a brittle type of mate-
rial with minimum conductivity. However, this laser machining can be used for all
kinds of materials in most cases. This chapter provides the principle of laser and its
types, mechanism of material removal using laser, applications, advantages, and
limitations of LBM.

Keywords: laser, monochromatic, machining, laser ablation, stimulated emission

1. Introduction

The growing product development for advanced applications such as aerospace,

automobiles, electronics and medical devices requires materials with high strength-
to-weight ratio. Advanced materials with superior properties are being developed
by researchers around the world for meeting the growing demand. The materials
such as nickel, titanium and their alloys, ceramics are known not only for high
strength-to-weight ratio but also for higher level of corrosion resistance, prolong-
ing capacity at higher temperatures with superior mechanical strength comparing
to other engineering materials [1]. These materials have greater properties such
as higher density and melting point, ductile, higher hardness and strength, hence
conventionally machining these materials is very challenging. Despite, it can be
machined using conventional techniques, but higher cutting forces and rigorous
tool wear attributes to huge cost in shaping these materials to the requirement.
Hence there were many unconventional machining processes (UMPs) developed to
replace conventional machining processes. One of the UMPs is laser beam machin-
ing (LBM) which is extensively used machining those difficult-to-machine materi-
als. LBM is considered suitable for machining hard materials LBM is characterized

1
Practical Applications of Laser Ablation

by independency to hardness property of work material. LBM is gaining attention

among the researchers and industry people because of its advantages such as higher
light intensity with low power requirement, good focusing property within short
duration of pulse, uniform heat distribution, eco-friendly nature which results
in accuracy in machining, narrow heat affected zone, increased productivity and
reduced manufacturing cost [2]. The upcoming sections describes in detail about
the principle of laser and its types, mechanism of laser machining, advantages,
applications and limitations of using LBM.

2. Principle of laser

The principle of Light amplification by stimulated emission of radiation

(LASER) was first hypothesized by Albert Einstein in the year of 1917 but it took
almost half a century to construct a working laser. Around 1960, a first experi-
mental setup of working industrial laser is developed. In many cases, the laser is
different from the normal light in a way that it carries photons of higher frequen-
cies. However, in some cases, the infrared laser has photons with low frequency
than normal light. The frequencies of all the photons contained in a laser light are
all same hence laser is characterized by coherence. The photons carried by a light
can stimulate the electrons in an atom therefore it emits same frequency photons
[3]. Based on this principle, laser produces high energy coherent light. Since laser
is the fundamental part of any laser-based system, it is essential to understand the
principle of laser light production.
Stimulation and amplification is the process (called as lasing) by which laser
system converts electrical energy into a light of high intensity energy. The medium
by which the lasing process carried out is called lasing medium. In any model of
an atom, positively charged nucleus is surrounded by negatively charged electrons
rotating at some specified path called orbits. The diameter and geometry of the
orbit vary based on many parameters including number of electrons, surrounded
magnetic field, structure of electrons and the existence of neighbor atoms. Every
electron presents in the orbital connected with a distinctive energy level. An atom
is said to be at ground level when it is at absolute zero temperature in which all the
electrons reside in their lowest potential energy. Energy from any exciting sources
such as electronic pulsation at higher temperature, chemical reaction or photon can
be absorbed by an electron at ground level. After absorbing the energy, it excites
to a higher energy level as schematically shown in Figure 1. Thus the movement of
electron from lower to higher energy level is accomplished. Upon reaching higher
energy levels, electron attains an unstable energy band. Immediately within very
short time (tens of nanosecond) it starts moving back to ground state by releasing

Figure 1.
Excitation between energy levels.

2
Laser Machining
DOI: http://dx.doi.org/10.5772/intechopen.93779

a photon and this process is termed as “spontaneous emission.” The frequency of

emitted photon would be equal to the frequency of exciting photon.
Sometime, when the electrons put into a meta-stable band due to energy change,
the electron stays in the higher energy level itself for a short time (micro to milli-
seconds). The state by which more number of electrons stays in meta-stable energy
level compared to the atoms in the ground level of a material is called “population
inversion.” These electrons are stimulated by suitable energy or frequency photons
to come back to ground state. Photons emission due to this stimulated return of
electrons is termed as “stimulated emission.” In this way, the emitted photons along
with one original photon temporarily having some spatial phase would create
coherent laser beam. From the schematic representation of stimulated absorption,
spontaneous emission, and stimulated emission as shown in Figure 2, position of
electrons in various energy levels are shown.

Figure 2.
Excitation between energy levels.

Figure 3.
Excitation between energy levels.

3
Practical Applications of Laser Ablation

The working of laser is schematically represented in Figure 3. A lasing medium

contained by a cylindrical glass container is closed using completely (100%) reflect-
ing mirror on one end and partially reflecting mirror on the other end. When the
glass vessel is exposed to a light using flash lamps, the photons of light excites the
atoms of lasing medium thus population inversion is obtained. Further due to
stimulated emission, photons are emitted. These stimulated photons in the longi-
tudinal direction form a high intense, coherent and highly directional laser beam.
Most of the stimulated photons would not be in the longitudinal direction and these
photons usually generate waste heat and finally lost.

3. Properties of laser

The distinctive properties of laser are coherence, highly monochromatic,

intensive radiance and directionality. These optical properties can be quantified for
analyzing the laser properties.

3.1 Coherence

The relationship between magnetic and electronic components of electromag-

netic wave refers to coherence property. The light beam is said to be coherent when
these components are properly aligned as shown in Figure 4. There are two terms of
coherence for a laser as spatial coherence and temporal coherence. Coherence is said
to be spatial when the correlation of phases happens at different points in a space
at a single point of time whereas in temporal coherence, correlation happens at
single point in a space over a time period. Figure 5 shows the concept of coherence.
Temporal coherence can be quantified through two important measures such as
coherence length and time. This property can be improved by run the laser in single
longitudinal and transverse mode.

3.2 Monochromatic

It is the most important property of laser and it can be measured by spectral

line width. When the range of emitted frequencies is small by a light source, it
is said to be high monochromatic. Laser beam normally have very few or single
spectral lines with highly narrow widths as shown in Figure 6. Monochromaticity
is most important because wide range of applications depends on this property
such as interferometry, velocimetry, holography, separation of isotope and com-
munications which require laser beam content. But this property is a not decisive
factor for machining.

Figure 4.
Components of electromagnetic wave.

4
Laser Machining
DOI: http://dx.doi.org/10.5772/intechopen.93779

3.3 Low-diffraction or collimation

Directionality is a property by which a light beam bends after passing sharp cor-
ners of objects. Diffraction or scattering of light at sharp edges increase the distance

Figure 5.
Schematic of spatially and temporally (a) coherent light and (b) incoherent light.

Figure 6.
Monochromaticity.

Figure 7.
Comparison of radiation from normal light bulb and a laser beam.

5
Practical Applications of Laser Ablation

from light source therefore certain amount of energy is lost. But laser beams possess
very low-diffraction property hence higher energy transfer can be effectively
achieved. This directional characteristic is useful when directing the laser beam for
machining applications.

3.4 Intensive radiance

The intensive radiance of a light is defined as the amount of power emitted per
unit area for a given solid angle. The unit for radiance is watts per square meter per
steradian. The angle by which a light beam is focused as a cone is called a solid angle.
Since the intensity of photons is high in laser beam, it can have high output powers.
Laser light source possess extreme amount of intensive radiance and transmitted
through a small solid edge angle. This property makes it very convenient to be
used for machining operations. Figure 7 gives the comparison of power density
­transmitted by normal light source and a laser [3].

4. Types of laser

Lasers are classified based on the state of lasing medium used and the temporal
mode. Based on the physical nature lasers are classified into solid-state lasers, gas
lasers, semiconductor, and liquid dye lasers [4]. Based on temporal mode, further
laser is categorized into two modes namely continuous wave (CW) and pulsed
mode. Continuous mode emits the laser beam continuously without interruption
whereas pulsed mode emits the laser beam periodically. Tables 1 and 2 shows the
important laser types along with their wavelengths.
In solid-state layers, the lasing medium is doped with very small number of
impurity ions. Maimam has developed the first solid-state laser during 1960 which
was a ruby laser. There are a number of laser types developed in the solid-state
category in which Nd:YAG is majorly used for LBM applications. Solid-state lasers
such as Nd:YAG, ruby and Nd-glass are highly used for machining metallic materi-
als. Nd:YAG lasers can also be used to ceramic materials. Gas lasers are grouped

Solid-sate lasers. Gas lasers

Lasing medium Wavelength (nm) Lasing medium Wavelength (nm)

Ruby 694 ArF 191

Alexandrite 700–820 KrF 249

Ti-sapphire 700–1100 XeCl 308

Nd-YLF 1047 XeF 351

Nd:YAG 1064 Argon 488, 514.5

Nd:glass 1062 Krypton 520–676

Er-YAG 2940 HeCd 441.5, 325

— — Copper vapor 510.6, 578.2

Gold vapor 628

HeNe 632.8

CO2 10,600

Table 1.
Solid-sate and gas lasers with their wavelengths.

6
Laser Machining
DOI: http://dx.doi.org/10.5772/intechopen.93779

Semiconductor lasers Liquid dye lasers

Lasing medium Wavelength (nm) Lasing medium Wavelength (nm)

AlGaInP 630–680 Stilbene 403–428

AlGaAs 780–880 Coumarin 102 460–515

InGaAs 980 Rhodamine 6G 570–640

InGaAsP 1150–1650 — —

Table 2.
Semiconductor and liquid dye lasers with their wavelengths.

into three categories based on the composition such as neutral atom, ion, and
molecular. Gas lasers generally can be of CW or pulsed mode lasers and available
with axial flow, transverse flow and folded axial flow in construction. CO2 laser is
the most commonly used gas laser for machining plastics, ceramics, nonmetals and
­sometimes organic materials also.
Semiconductor lasers, though made of solid materials the working principle are
different from solid-state lasers. It is based on radiative recombination of charge
carriers. Unique characteristic of a semiconductor laser is that they are capable of
producing wide beam divergence angles around 40°. Comparing to other types of
lasers, liquid-state lasers are easier to fabricate. Main advantages of liquid-state
lasers are ease cooling and replenishment in laser cavities. Spectral properties of
liquid organic molecules enable liquid dye lasers to get tuned within wide range of
wavelengths from 200 nm to 1000 nm. The detailed working principles of these
lasers are beyond the scope of this chapter and can be found in any standards texts.

5. Material removal using laser

5.1 Construction of LBM

Laser beam machining is a nonconventional, advanced machining process

wherein there are essential parts required to construct a complete LBM setup. A
pumping medium or lasing medium that contains large quantity of atoms is a pri-
mary component to produce laser light. For exciting the atoms in lasing medium, a
flash lamp or flash tube is needed and it should be connected to the controlled high
voltage power supply. Based on the type of operating mode (either pulsed mode or
CW) a capacitor can be integrated to the power circuit. A typical solid-state LBM
setup is schematically shown in Figure 8.

5.2 Mechanism of material removal in LBM

Laser based machining processes is identified as a material removal technique

in industrial application. Materials removal is accomplished by the interaction
between the laser beam and work material. It is severely a localized thermal process.
Higher amount of light energy is received by base material and then higher heat
is created between the locality of interaction while hitting the laser source on the
base material. Due to highly elevated temperature at the beam spot, the material
becomes soft, melt, burn and vaporized. Additionally, the interaction of laser
beams and work material is associated with the material removal by photochemical
process which is often called photo ablation. Figure 9 schematically represents the
effects of laser beam-work material interaction [5].

7
Practical Applications of Laser Ablation

Figure 8.
Laser beam machining setup.

Figure 9.
Laser beam-work material interactions: (a) heating, (b) melting of surface, (c) vaporization of surface,
(d) formation of plasma, and (e) ablation.

The parameters of LBM such as intensity of laser light, distribution of beam,

spot size, scanning speed, and relative motion between laser beam and work piece
can be changed according to the requirements for different work materials. As
presented in the introduction section, lasers are replacing conventional machining
processes due to many advantages. Many developments have been made in the laser
technology to shorten the pulse time for different machining processes. Longer
pulse duration increases the heat affected zone (HAZ) and leaves high thermal

8
Laser Machining
DOI: http://dx.doi.org/10.5772/intechopen.93779

Figure 10.
Difference between the effects of (a) long-pulsed and (b) short-pulsed lasers.

stresses resulting in crack and void formation, and surface debris. Short pulse dura-
tion leads to lesser thermal conduction thus resulting in precise machining opera-
tion and good surface finish. Figure 10 shows the difference between the effects of
long and short pulse durations [6].

5.3 Types of LBM techniques

Machining using laser is generally categorized into three types namely one-
dimensional, two-dimensional and three-dimensional machining processes. In one
dimensional machining process, the laser beam will have no relative motion with
the work piece material. In this relatively stationary arrangement, the erosion front
is located at the work piece and focused laser beam removes the material in the path
it propagates through which is a straight line. Hence one-dimensional LBM process
is generally used for drilling applications. In contrast, the work piece also will move
along with laser source in two-dimensional LBM process. The erosion front placed
on the beam edge and the material removal happens in a two-dimensional plane

Figure 11.
Schematic of (a) one-dimensional (drilling), (b) two-dimensional (cutting), and (c) three-dimensional
(milling) machining operations.

9
Practical Applications of Laser Ablation

resulting in a creation of two-dimensional surface as shown in Figure 11. Two-

dimensional LBM is most suitable for cutting operations. Three-dimensional LBM
uses two or more sources of laser beams. Each laser beam forms two-dimensional
surfaces according to their relative motion with the work piece. When the surfaces
formed by each laser beams intersects a three-dimensional space is created that
defines the shape of material to be removed. Three-dimensional LBM process is
generally used for milling process. For better understanding of different types of
LBM processes a schematic representation is given in Figure 11 [7].

6. Applications

In general, the use of lasers found in many applications includes chemical,

biochemical, optics, medical, military operations, polymer sciences, nuclear
physics [8–12] and so on. In manufacturing, lasers are successfully applied for
material removal, metal joining, cladding and alloying processes. Specifically, this
chapter discusses the material removal applications of lasers. Drilling, grooving,
cutting, three-dimensional machining operations such as lathe and milling opera-
tions, micro machining and laser assisted machining processes are the extended
­applications of lasers in LBM [3].

6.1 Drilling using LBM

One of the major advantages in drilling using lasers compared to conventional

machining process is the aspect ratio (max 1:20) and small size of the hole drilled.
Both continuous and pulse laser are used for drilling operations in which pulsed
laser gives lesser plasma generation. The types of drilling operations that can be
performed using LBM are single-pulsed drilling, percussion drilling, trepanning
and helical drilling. When laser beam is focused into the material, the temperature
is created by absorbing the photons. The material melts and vaporizes when the
temperature exceeds the melting temperature of the material. If the radiation of
laser is set lesser than particular threshold (106 W/cm2 for steels), the material
melts but not vaporizes and using a jet of gas the molten material is ejected [13].
The single pulse drilling process makes either through or blind holes with less than
1:15 aspect ratio. This is a rapid drilling process mainly suitable where produc-
tion rate is more important than quality. Single pulse drilling is mostly adapted in
automotive industry for processing connecting rods and filters. Percussion drilling
uses pulsed-lasers’ focus on the same spot to produce a hole while maintaining a
balance between throughput and quality. Due to major advantages like its precision
and quick processing capability, percussion drilling is adapted in making holes in
the blades of turbine-airfoil. Though it has major advantages, there are drawbacks
reported such as dross, spatter, and tapering.
Trepanning technique is another hole making technique where the material
removal is performed on the circumference of any circle to make holes of higher
diameters. It is considered to be a standard technique for making holes around 500
micrometers diameter. The nanosecond pulsed laser source is utilized for material
removal around the circumference hence the drawbacks of percussion drilling
remains in this application also. Trepanning technique reduces the taper effect and
produces more jagged edge quality. To overcome the drawbacks of trepanning a
relatively new technique called helical drilling is introduced. Helical drilling follows
multitude ablation steps. The advantages of helical drilling over trepanning using
percussion drilling are improved circularity of drilled holes, minimized loads on
opposite walls and more importantly reduced recast layers or sometimes completely

10
Laser Machining
DOI: http://dx.doi.org/10.5772/intechopen.93779

Figure 12.
Schematic of laser drilling.

avoided. Helical drilling is more preferred in the case of laser beam diameter is very
near to helical diameter at focus point. Energy balance is important in laser drilling
among the energy released by laser beam, energy absorbed by material, energy lost
to the surrounding and the energy utilized for melting (phase changing) the mate-
rial as shown in Figure 12.

6.2 Cutting using LBM

Cutting is an essential operation in any material removal processes. A relative

motion between work piece and the laser beam is required to produce a two-
dimensional working plane where the material removal takes place. During relative
motion of laser beam and work piece, a kerf is produced which removes the mate-
rial in its path. Complex two-dimensional shapes can be cut from the flat work piece

Figure 13.
LBM for cutting operation.

11
Practical Applications of Laser Ablation

Figure 14.
Three-dimensional LBM for (a) lathe operation and (b) milling operation.

materials where mechanism of material removal is similar to drilling operation.

In contrast to the drilling process, the erosion front is located at the front of line
of laser beam as shown in Figure 13. However, the temperature field and erosion
front is fixed based on the coordinate moves along with produced laser source that
ensures steady state process. The erosion front molten material is flushed away
using a gas jet during the cutting process.

6.3 Three-dimensional LBM

Three-dimensional LBM uses two or more number of laser beams simultane-

ously focused to obtain an intersected volume for material removal. To precisely
create such volumes with relative motions, highly accurate optical manipulating
systems are therefore necessary. Recent systems equipped with optical scanning
systems have high level of control over the motion of laser beams which enables
efficient and effective machining operations. The material removal using these
tools is referred as 3-dimensional (3D) laser material processing. In general, the
3D laser material processing is grouped into various categories such as laser beams
along with 3D LBM, 5-axis heads along with 3D processing workstation and 3D
remote laser processing. Figure 14 illustrate the graphical picture of two-beam laser
machining processes for lathe and milling operations. Each beam creates a groove
like volume of material removal when they intersect with some incidence angle. The
incidence angle may be changed and dynamically varied along with relative motion
to get intricate shapes of machining.
LBM is successfully adapted in micromachining field due to its high flexibility
to automation and high degree of radiance. Laser beam micromachining is capable
of producing parts with sizes ranging from micro to sub-micro scales. It usually
employs the pulsed lasers with an average power of less than 1 kW. The pulses of
femtosecond duration are widely used for micromachining. Micromachining can be
performed on wide range of materials such as metals, glasses, diamond and other
difficult to machining materials. Laser-assisted manufacturing (LAM) is another
technique helps to enhance the maximum productivity, quality with minimized
machine tool vibrations, machining forces and tool wear. LAM is also an effective
technique to machine brittle materials without cracks and failure. This hybrid
machining process, laser beam is focused on the work piece just before the cutting
tool engages. Scanning of laser initially heats up the work therefore helps in plastic
deformation rather than brittle deformation during machining. The LAM processes
are suitable for brittle and hard type of material such as ceramics, nickel alloys and
the higher amount of silicon element material.

12
Laser Machining
DOI: http://dx.doi.org/10.5772/intechopen.93779

7. Advantages

LBM is an excellent manufacturing technique to process wide ranges of difficult

to machine materials especially ceramics and advanced composite materials. LBM
technique is capable of machining intricate shapes that cannot be reached or pro-
cessed by conventional machining processes. LBM is an alternate to conventional
machining processes due to many advantages as follow:

• Due to precise machining capability, LBM can produce excellent surface finish
therefore post processing can be eliminated.

• LBM is a clean manufacturing technique due to less environment pollution and

no requirement of chemicals or solvents for machining.

• LBM can be easily automated for higher productivity and to achieve high speed
machining.

• It uses no cutting tool therefore no cutting forces involved during machining.

This phenomenon helps to avoid heavy construction of machine tools, physical
damages, vibrations, frequent tooling requirements.

• Degree of accuracy in machining complex geometry is high.

• LBM depends on thermal and few optical properties of work material rather
than mechanical properties such as hardness and brittleness. As a result, most
of the materials with any degree of mechanical properties with lower diffusiv-
ity and conductivity can be machined.

• Wide range of materials from plastics to diamond can be machined.

• Residual stresses caused due to HAZ are very less in LBM.

• Machining micro features with large aspect ratio is possible with LBM.

8. Limitations

There are many issues and limitations associated with the aforementioned LBM
technique. The major issues are produced accuracy, achieved surface quality and
rate of material removal. The erosion front is the main factor decides the amount of
material removal in LBM technique. In one-dimensional machining, the speed of
propagation in erosion front in the straight line decides the rate of material removal.
In another hand, the scanning speed plays a significant role in metal removal during
the two-dimensional machining processes. Similarly, the laser scanning speed is
produced the intersecting surfaces for volume formation and the decisive factor
for material removal rate during the 3D machining processes. Controlling the LBM
parameters for a balanced and effective machining is a real challenge faced by
industries. Secondly, the dimensional accuracy is affected by the kerf shape of laser
which leads to tapered holes instead of narrow holes. Surface quality is the other
important aspect of machining, which is measured by surface roughness, formation
of dross and the HAZ. Since LBM is completely thermal based machining process it
also has several limitations such as,

13
Practical Applications of Laser Ablation

• Minimum amount of metal removal

• Investment cost is high

• Highly skilled operator is required

• Maintenance cost is high

• Power consumption for LBM is high

• Transparent and greatly reflective materials cannot be machined using LBM

• Applications related to machining thicker materials are very limited

9. Conclusions

The chapter presented an overview of the LBM technique and the principle
of laser production, properties, types of lasers, and its application in machin-
ing field. The advantages and limitations are also discussed at the end. Based on
the discussions from the presented sections, the following conclusions are made
regarding LBM.

• LBM is an effective technique for processing complex geometries of different

materials with superior properties. While this technique is mostly advanta-
geous in the field of machining, it also possesses few disadvantages such as low
energy efficiency, low material removal rate which affects productivity, quality
concern due to diverged or converged laser beam.

• LBM depends upon many important parameters such as wavelengths of lasers

used, scanning speed, type of laser beam (pulsed or CW), pulse duration,
assist gas and its flow, material properties and physical dimensions to assess
some of the performance characteristics like surface quality, thermal stresses
due to HAZ, formation of dross and defects.

• Excellent flexibility to automation of LBM enables it to be used in advanced

machining applications like micromachining with superior level of accuracy.

Acknowledgements

The authors wish to thank the Ministry of Science and Technology, Taiwan ROC
for the financial support to carry out this work.

Conflict of interest

The authors declare that they have no conflicts of interest in the work.

14
Laser Machining
DOI: http://dx.doi.org/10.5772/intechopen.93779

Author details

Natarajan Jeyaprakash1*, Che-Hua Yang1,2 and Manickam Bhuvanesh Kumar3

1 Additive Manufacturing Center for Mass Customization Production,

National Taipei University of Technology, Taipei, Taiwan, ROC

2 Institute of Manufacturing Technology, National Taipei University of Technology,

Taipei, Taiwan, ROC

3 Department of Production Engineering, National Institute of Technology

Tiruchirappalli, India

*Address all correspondence to: prakash84gct@gmail.com; prakash@ntut.edu.tw

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms
of the Creative Commons Attribution License (http://creativecommons.org/licenses/
by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,
provided the original work is properly cited.

15
Practical Applications of Laser Ablation

References

[1] Nagimova A, Perveen A. A review [10] Moore CB. Chemical and

on laser machining of hard to cut Biochemical Applications of Lasers V1.
materials. Materials Today: Proceedings. Vol. 1. United States: Elsevier; 2012
2019;18:2440-2447
[11] Murnick DE, Feld MS. Applications
[2] Kuar A, Doloi B, Bhattacharyya B. of lasers to nuclear physics. Annual
Modelling and analysis of pulsed Nd: Review of Nuclear and Particle Science.
YAG laser machining characteristics 1979;29(1):411-452
during micro-drilling of zirconia
(ZrO2). International Journal of [12] Vij D, Mahesh K. Medical
Machine Tools and Manufacture. Applications of Lasers. United States:
2006;46(12-13):1301-1310 Springer Science & Business Media;
2013
[3] Chryssolouris G. Laser Machining:
Theory and Practice. New York, United [13] Ready J. LIA Handbook of
States: Springer-Verlag; 2013 Laser Materials Processing. Berlin,
Heidelberg, German: Springer-Verlag;
[4] Dahotre NB, Harimkar S. Laser 2001
Fabrication and Machining of Materials.
United States: Springer Science &
Business Media; 2008

[5] Chryssolouris G, Stavropoulos P,

Salonitis K. Process of laser machining.
In: Nee A, editor. Handbook of
Manufacturing Engineering and
Technology. London: Springer London;
2013. pp. 1-25

[6] Agrawal R, Wang C. Laser

Beam Machining. In: Encyclopedia
of Nanotechnology. 2nd ed. The
Netherlands: Springer; 2016.
pp. 1739-1753

[7] Chryssolouris G, Anastasia N,

Sheng P. Three-dimensional laser
machining for flexible manufacturing.
In: Conference on Laser Application in
the Automotive Industries. Aachen: SAE
International; 1991. pp. 247-253

[8] Chow WW, Jahnke F. On the

physics of semiconductor quantum
dots for applications in lasers and
quantum optics. Progress in Quantum
Electronics. 2013;37(3):109-184

[9] Kaushal H, Kaddoum G. Applications

of lasers for tactical military operations.
IEEE Access. 2017;5:20736-20753

16