final report

A STUDY ON THE APPLICATION OF LASER TECHNOLOGY
Chapter 1
Introduction
A laser is a device that emits light through a process of optical amplification based on
the stimulated emission or electromagnetic radiation. The term "laser" originated
as acronyms for Light Amplification by Stimulated Emission of Radiation.
Lasers differ from other sources of light because they emit light coherently. Spatial
coherence allows a laser to be focused to a tight spot, enabling applications like laser cutting
and lithography. Spatial coherence also allows a laser beam to stay narrow over long
distances (collimation), enabling applications such as laser pointers.
Lasers can also have high temporal coherence which allows them to have a very
narrow spectrum i.e., they only emit a single color of light. Temporal coherence can be used
to produce pulses of light—as short as a femto second.
Fig.1.1 laser light
Laser beams can be focused to very tiny spots, achieving a very high irradiance, or they can
be launched into beams of very low divergence in order to concentrate their power at a large
distance.
Lasers are distinguished from other light sources by their coherence. Spatial coherence is
typically expressed through the output being a narrow beam which is diffraction- limited,
often a so-called "pencil beam." Laser beams can be focused to very tiny spots, achieving a
very high irradiance, or they can be launched into beams of very low divergence in order to
concentrate their power at a large distance.
ME-DEPARTMENT SRMGPC LKO 1 | P a g e

Properties of laser
1. The light emitted by lasers is different from that produced by more common light sources
such as incandescent bulbs, fluorescent lamps, and high-intensity arc lamps. An
understanding of the unique properties of laser light may be achieved by contrasting it
with the light produced by other, less unique sources.
2. Highly directional nature of light produced by a laser. "Directionality" is the
characteristic of laser light that causes it to travel in a single direction within a narrow
cone of divergence.
3. It consists of an extremely narrow range of wavelengths within the red portion of the
spectrum. It is said to nearly monochromatic, meaning that it consists of light of almost
single wavelength.
4. Coherence is the most fundamental property of laser light and distinguishes it from the
light from other sources. Thus, a laser may be defined as a source of coherent light. So
that laser light is highly coherent, means that phases at every instant of time are always
same.
Fig. 1.2
First, let's discuss the properties of laser light and then we will go into how is
created. Laser light is monochromatic, directional, and coherent.
Fig.1.3

Chapter 2
History of laser
Max Plank published work in 1900 that provided the understanding that light is a form of
electromagnetic radiation. Without this understanding the laser would not have been
invented.
The principle of the laser was first known in 1917, when physicist Albert Einstein described
the theory of stimulated emission. However, it was not until the late 1940s that engineers
began to utilize this principle for practical purposes. At the onset of the 1950’s several
different engineers were working towards the harnessing of energy using the principal of
stimulated emission.
At the University of Columbia was Charles Townes, at the Univers ity of Maryland was
Joseph Weber and at the Lebedev Laboratories in Moscow were Alexander Prokhorov and
Nikolai G Basov. At this stage the engineers were working towards the creation of what was
termed a MASER (Microwave Amplification by the Stimulated Emission of Radiation),
A device that amplified microwaves as opposed to light and soon found use in microwave
communication systems. Townes and the other engineers believed it to be possible to create
an optical maser,
A device for creating powerful beams of light using higher frequency energy to stimulate
what was to become termed the lasing medium. Despite the pioneering work of Townes and
Prokhorov it was left to Theodore Maiman in 1960 to invent the first Laser using a lasing
medium of ruby that was stimulated using high energy flashes of intense light.
Townes and Prokhorov were later awarded the Nobel Science Prize in 1964 for their
endeavors.
Fig 2.1 scientist who developed laser
The Laser was a remarkable technical breakthrough, but in its early years it was something of
a technology without a purpose. It was not powerful enough for use in the beam weapons
envisioned by the military, and its usefulness for transmitting information through the
atmosphere was severely hampered by its inability to penetrate clouds and rain. Almost
immediately, though, some began to find uses for it. Maiman and other engineers developed
laser weapons sighting systems and powerful lasers for use in surgery and other.

Albert Einstein first explained the theory of stimulated emission in 1917, which became the
basis of Laser. He postulated that, when the population inversion exists between upper and
lower levels among atomic systems, it is possible to realize amplified stimulated emission
and the stimulated emission has the same frequency and phase as the incident radiation.
However, it was in late 1940s and fifties that scientists and engineers did extensive work to
realize a practical device based on the principle of stimulated emission. Notable scientists
who pioneered the work include Charles Townes, Joseph Weber, Alexander Prokhorov and
Nikolai G Basov.
Initially, the scientists and engineers were working towards the realization of a MASER
(Microwave Amplification by the Stimulated Emission of Radiation) ; a device that amplified
microwaves for its immediate application in microwave communication systems. Townes
and the other engineers believed it to be possible create an optical maser, a device for
creating powerful beams of light using higher frequency energy to stimulate what was to
become termed the lasing medium. Despite the pioneering work of Townes and Prokhorov it
was left to Theodore Maiman in 1960 to invent the first Laser using ruby as a lasing medium
that was stimulated using high energy flashes of intense light.
The development of Lasers has been a turning point in the history of science and engineering.
It has produced a completely new type of systems with potentials for applications in a wide
variety of fields. During sixties, lot of work had been carried out on the basic development of
almost all the major lasers including high power gas dynamic and chemical lasers. Almost all
the practical applications of these lasers in defense as well as in industry were also identified
during this period. The motivation of using the high power lasers in strategic scenario was a
great driving force for the rapid development of these high power lasers. In early seventies,
megawatt class carbon dioxide gas dynamic laser was successfully developed and tested
against typical military targets. The development of chemical lasers, free electron and X-ray
lasers took slightly longer time because of involvement of multidisciplinary approach.
The major steps of advances or breakthroughs in Laser research are given below: Dates,
Contributors and events:
1917: Einstein, A. - Concept and theory of stimulated light emission
1948: Gabor, D. - Invention of holography
1951: Charles H Townes, Alexander Prokhorov, Nikolai G Basov, Joseph Weber - The
invention of the MASER (Microwave Amplification of Stimulated Emission of Radiation) at
Columbia University, Lebedev Laboratories, Moscow and University of Maryland.
1956: Bloembergen, N. - Solid-state maser- [Proposal for a new type of solid state maser] at
Harvard University.
1958: Schawlow, A.L. and Townes, C.H. - Proposed the realization of masers for light and
infrared at Columbia University.

1960: Maiman, T.H. - Realization of first working LASER based on Ruby at Hughes
Research Laboratories.
1961: Javan, A., Bennet, W.R. and Herriot, D.R. - First gas laser: Helium- Neon (He-Ne
laser) at Bell Laboratories.
1961: Fox, A.G., Li, T. - Theory of optical resonators at Bell Laboratories.
1962: Hall,R. - First Semiconductor laser (Gallium-Arsenide laser) at General Electric Labs.
1962: McClung,F.J and Hellwarth, R.W. - Giant pulse generation / Q-Switching.
1962: Johnson, L.F., Boyd, G.D., Nassau, K and Sodden, R.R. - Continuous wave solid-state
laser.
1964: Geusic, J.E., Markos, H.M., Van Uiteit, L.G. - Development of first working Nd:YAG
LASER at Bell Labs.
1964: Patel, C.K.N. - Development of CO2 LASER at Bell Labs.
1964: Bridges, W. - Development of Argon Ion LASER a Hughes Labs.
1965: Pimentel, G. and Kasper, J. V. V. - First chemical LASER at University of California,
Berkley.
1965: Bloembergen, N. - Wave propagation in nonlinear media.
1966: Silfvast, W., Fowles, G. and Hopkins - First metal vapor LASER - Zn/Cd - at
University of Utah.
1966: Walter, W.T., Solomon, N., Piltch, M and Gould, G. - Metal vapor laser.
1966: Sorokin, P. and Lankard, J. - Demonstration of first Dye Laser action at IBM Labs.
1966: AVCO Research Laboratory, USA. - First Gas Dynamic Laser based on CO2
1970: Nikolai Basov's Group - First Excimer LASER at Lebedev Labs, Moscow based on
Xenon (Xe) only.
1974: Ewing, J.J. and Brau, C. - First rare gas halide excimer at Avco Everet Labs.
1977: John M J Madey's Group - First free electron laser at Stanford University.
1977: McDermott, W.E., Pehelkin, N.R,. Benard, D.J and Bousek, R.R. - Chemical Oxygen
Iodine Laser (COIL).
1980: Geoffrey Pert's Group - First report of X-ray lasing action, Hull University, UK.
1984: Dennis Matthew's Group - First reported demonstration of a "laboratory" X-ray laser
from Lawrence Livermore Labs.
1999: Herbelin,J.M., Henshaw, T.L., Rafferty, B.D., Anderson, B.T., Tate, R.F., Madden,
T.J., Mankey II, G.C and Hager, G.D. - All Gas-Phase Chemical Iodine Laser (AGIL).
2001: Lawrence Livermore National Laboratory - Solid State Heat Capacity Laser (SSHCL).

Development of lasernd Stimulated Light
1. In 1905 German scientist Albert Einstein announced his own theory about light, namely
that it is made up of both particles and waves. Einstein claimed that the particles, called
photons (from the Greek word for "light"), move along in wavelike patterns. Later, other
scientists performed experiments that proved Einstein was right. Einstein himself then
went on to predict some more startling things about light, first and foremost how photons
are made. He agreed with some other scientists of his day about how light sources (like
candles, light bulbs, or the sun) produce photons. The researchers thought that atoms (the
tiny particles that make up all material in the universe) give off photons. Some form of
energy—such as heat, electricity, or chemical energy—might "excite" an atom, or make it
more energetic. It would then emit (give off) a photon. Afterward, the atom would go
back to its normal, unexcited state. Because there are huge numbers of atoms, they give
off equally large numbers of photons. A 100-watt light bulb gives off about 10 trillion
photons every second.
2. 1951, while sitting on a park bench, Townes had a brilliant idea. He realized it might be
possible to use molecules of ammonia to produce a powerful microwave beam. (A
molecule consists of two or more atoms that are connected together.) Townes reasoned
Charles Townes (left) and James P. Gordon proudly display their maser, a device that
greatly amplifies microwaves. That when molecules of ammonia became excited (by
heat, electricity, or chemical energy), they could be stimulated to emit microwaves of the
type he was working with. He knew this process would be almost identical to the one
Einstein described for stimulating visible light. The only difference was that Townes
would be using microwaves instead of light. He calculated that if the ammonia molecules
could be kept in an excited state long enough, they might be stimulated to produce more
and more microwaves. Eventually, the waves would become concentrated and more
powerful. In short, the microwaves would be amplified.Townes decided to try to build a
working model. He enlisted the aid of two other researchers, Herbert J. Zigler and James
P. Gordon. Working diligently, by 1954 the three men had a working device that operated
in the following way: First, some ammonia gas was heated until many of the molecules
became excited and then were separated from the unexcited molecules. Next, the excited

molecules flowed into a chamber called the resonant cavity (or resonator) where the
stimulation of the molecules took place. As the excited ammonia molecules began to emit
microwave particles, the particles began to bounce back and forth inside the chamber.
When one of these particles came near an excited molecule, the molecule suddenly gave
off its own particle. Thus the particles themselves stimulated the production of more
particles. Soon the number of particles doubled, and then doubled again and again until
the microwaves in the chamber had become very powerful.
3. By 1960 many scientists, including Townes and Schawlow, Basov and Prokhorov, and
Gould, had asked for laser patents. In addition, the paper published by Townes and
Schawlow had caused widespread interest in lasers in the American scientific
community. Researchers in labs around the country raced to be first to construct a
working model. The first successful device appeared on July 7, 1960, built by a
previously unknown researcher who had worked totally on his own—Theodore H.
Maiman of the Hughes Aircraft Company in Malibu, California. Maiman's laser was
small (only a few inches long) and not very complicated. The core of the device consisted
of an artificial ruby about one and a half inches long, so Maiman called his invention the
"ruby laser."
4. The first gas laser (helium neon) was invented by Ali Javan, in 1960. The gas laser was
the first continuous-light laser and the first to operate "on the principle of converting
electrical energy to a laser light output." It has been used in many practical applications.
5. In 1962, Robert Hall, created a revolutionary type of laser that is still used in many of the
electronic appliances and communications systems that we use every day.
Fig. 2.2 laser research center

Chapter 3
Components of laser
All Lasers are comprised of these essential medium
Every laser have a three basic components are;
1 Active medium.
2 External source.
3 Optical resonator.
Fig.3.1 components of laser
1. The active medium is excited by the external energy source (pump source) to produce
population inversion. In the gain medium that spontaneous and stimulated emission of
photons takes place, leading to the phenomenon of optical gain, or amplification.
Semiconductors, organic dyes, gases (He, Ne, CO2, etc.), solid materials ( YAG,
sapphire(ruby) etc.) are usually used as lasing materials and often LASERs are named for
the ingredients used as medium.
2. The excitation source, pump source provides energy which is needed for the
population inversion and stimulated emission to the system. Pumping can be done in two
ways – electrical discharge method and optical method. Examples of pump sources are

electrical discharges, flash lamps, arc lamps, light from another laser, chemical reactions
etc.
3. Resonator guide basically provides the guidance about the simulated emission process.
It is induced by high speed photons. Finally, a laser beam will be generated.
In most of the systems, it consists of two mirrors. One mirror is fully reflective and other
is partially reflective. Both the mirrors are set up on optic axis, parallel to each other. The
active medium is used in the optical cavity between the both mirrors. This arrangement
only filters those photons which came along the axis and others are reflected by the
mirrors back into the medium, where it may be amplified by stimulated emission.
Electrons in the atoms of the lasing material normally reside in a steady-state lower energy
level. When light energy from the flash lamp is added to the atoms of the lasing material, the
majority of the electrons are excited to a higher energy level -- a phenomenon known as
population inversion. This is an unstable condition for these electrons. They will stay in this
state for a short time and then decay back to their original energy state. This decay occurs in
two ways: spontaneous decay -- the electrons simply fall to their ground state while emitting
randomly directed photons; and stimulated decay -- the photons from spontaneous decaying
electrons strike other excited electrons which causes them to fall to their ground state. This
stimulated transition will release energy in the form of photons of light that travel in phase at
the same wavelength and in the same direction as the incident photon. If the direction is
parallel to the optical axis, the emitted photons travel back and forth in the optical cavity
through the lasing material between the totally reflecting mirror and the partially reflecting
mirror. The light energy is amplified in this manner until sufficient energy is built up for a
burst of laser light to be transmitted through the partially reflecting mirror.
As shown in figure 4, a lasing medium must have at least one excited (metastable) state
where electrons can be trapped long enough (microseconds to milliseconds) for a population
inversion to occur. Although laser action is possible with only two energy levels, most lasers
have four or more levels.

Fig. 3.2 Three level laser energy diagram
A Q-switch in the optical path is a method of providing laser pulses of extremely short time
duration. A rotating prism like the total reflector in figure 3 was an early method of providing
Q-switching. Only at the point of rotation when there is a clear optical path will light energy
be allowed to pass.
A normally opaque electro-optical device (e.g., a pockets cell) is now often used for a Q-switching
device. At the time of voltage application, the device becomes transparent; the
light built up in the cavity by excited atoms can then reach the mirror so that the cavity
Quality, Q, increases to a high level and emits a high peak power laser pulse of a few
nanoseconds duration.
When the phases of different frequency modes of a laser are synchronized (locked together),
these modes will interfere with each other and generate a beat effect. The result is a laser
output with regularly spaced pulsations called "mode locking". Mode locked lasers usually
produce trains of pulses with a duration of a few picoseconds to nanoseconds resulting in
higher peak powers than the same laser operating in the Q-switched mode.
Pulsed lasers are often designed to produce repetitive pulses. The pulse repetition frequency,
PRF, as well as pulse width is extremely important in evaluating biological effects.

Chapter 4
Types of laser
1. Semiconductor laser
The laser diode is a light emitting diode with an optical cavity to amplify the light emitted
from the energy band gap that exists in semiconductors as shown in figure 11. They can be
tuned by varying the applied current, temperature or magnetic field.
Fig.4.1 Semiconductor laser diagram
2. Gas laser
Gas lasers consist of a gas filled tube placed in the laser cavity as shown in figure 12. A
voltage (the external pump source) is applied to the tube to excite the atoms in the gas to a
population inversion. The light emitted from this type of laser is normally continuous wave
(CW). One should note that if Brewster angle windows are attached to the gas discharge
tube, some laser radiation may be reflected out the side of the laser cavity. Large gas lasers
known as gas dynamic lasers use a combustion chamber and supersonic nozzle for
population inversion.
Fig.4.2 Gas laser diagram

3. Dye laser
Figure 13 shows a dye laser diagram. Dye lasers employ an active material in a liquid
suspension. The dye cell contains the lasing medium. Many dyes or liquid suspensions are
toxic.
Fig.4.3 Common Dye Laser Diagram
4. Free electron laser
Free electron lasers such as in figure 14 have the ability to generate wavelengths from the
microwave to the X-ray region. They operate by having an electron beam in an optical cavity
pass through a wiggler magnetic field. The change in direction exerted by the magnetic field
on the electrons causes them to emit photons.

Fig.4.4 Free Electron Laser Diagram
5. Transverse electromagnetic laser
Laser beam geometries display transverse electromagnetic (TEM) wave patterns across the
beam similar to microwaves in a wave guide. Figure 9 shows some common TEM modes in
a cross section of a laser beam.
Fig.4.5 Common TEM laser beam modes
A laser operating in the mode could be considered as two lasers operating side by
side. The ideal mode for most laser applications is the mode and this mode is
normally assumed to easily perform laser hazards analysis. Light from a conventional light
source is extremely broadband (containing wavelengths across the electromagnetic
spectrum). If one were to place a filter that would allow only a very narrow band of
wavelengths in front of a white or broadband light source, only a single light color would be
seen exiting the filter. Light from the laser is similar to the light seen from the filter.
However, instead of a narrow band of wavelengths none of which is dominant as in the case
of the filter, there is a much narrower line width about a dominant center frequency emitted
from the laser. The color or wavelength of light being emitted depends on the type of lasing
material being used. For example, if a Neodymium: Yttrium Aluminum Garnet (Nd:YAG)
crystal is used as the lasing material, light with a wavelength of 1064 nm will be emitted.
Table 1 illustrates various types of material currently used for lasing and the wavelengths that
are emitted by that type of laser. Note that certain materials and gases are capable of emitting
more than one wavelength. The wavelength of the light emitted in this case is dependent on
the optical configuration of the laser.

Table 1 Common Lasers and Their Wavelengths
LASER TYPE
WAVELENGTH
(Nanometers)
Argon Fluoride 193
Xenon Chloride 308 and 459
Xenon Fluoride 353 and 459
Helium Cadmium 325 - 442
Rhodamine 6G 450 - 650
Copper Vapor 511 and 578
Argon
457 - 528 (514.5 and 488
most used)
Frequency doubled Nd:YAG 532
Helium Neon 543, 594, 612, and 632.8
Krypton
337.5 - 799.3 (647.1 - 676.4
most used)
Ruby 694.3
Laser Diodes 630 - 950
Ti:Sapphire 690 - 960
Alexandrite 720 - 780
Nd:YAG 1064
Hydrogen Fluoride 2600 - 3000
Erbium:Glass 1540
Carbon Monoxide 5000 - 6000
Carbon Dioxide 10600
Light from a conventional light source diverges or spreads rapidly show in fig 16. The
intensity may be large at the source, but it decreases rapidly as an observer moves away from
the source.

Figure 4.6 Divergence of Conventional Light Source
In contrast, the output of a laser as shown in figure 17 has a very small divergence and can
maintain high beam intensities over long ranges. Thus, relatively low power lasers are able to
project more energy at a single wavelength within a narrow beam than can be obtained from
much more powerful conventional light sources.
Fig.4.7 Divergence of Laser Source
For example, a laser capable of delivering a 100 mJ pulse in 20 ns has a peak power of 5
million watts. A CW laser will usually have the light energy expressed in watts, and a pulsed
laser will usually have its output expressed in joules. Since energy cannot be created or
destroyed, the amount of energy available in a vacuum at the output of the laser will be the
same amount of energy contained within the beam at some point downrange (with some loss
in the atmosphere).

Fig. illustrates a typical laser beam. The amount of energy available within the sampling
area will be considerably less than the amount of energy available within the beam. For
example, a 100 mW laser output might have 40 mW measured within 1 sample area.
The irradiance in this example is 40 mW/ .
Fig.4.8 Illustration of Irradiance

Chapter 5
Working of laser
The electromagnetic spectrum consists of the complete range of frequencies from radio
waves to gamma rays. All electromagnetic radiation consists of photons which are individual
quantum packets of energy. For example, a household light bulb emits about
1,000,000,000,000,000,000,000 photons of light per second! In this course we will only
concern ourselves with the portion of the electromagnetic spectrum where lasers operate -
infrared, visible, and ultraviolet radiation.
Name Wavelength
Ultraviolet 100 nm - 400 nm
Visible 400 nm - 750 nm
Near Infrared 750 nm - 3000 nm
Far Infrared 3000 nm - 1 mm
Einstein was awarded the Nobel Prize for his discovery and interpretation of the formula -
E=mc2 - right? Wrong.
Fig 5.1Albert Einstein
He won the Nobel Prize for his explanation of the phenomena referred to as the photoelectric
effect. When light (electromagnetic energy) is shined on a metal surface in a vacuum, it may

free electrons from that
surface.
Fig.5.2
These electrons can be detected as a current flowing in the vacuum to an electrode.
The light was not always strong enough to cause this effect, however. When the scientists
made the light brighter, no increase in electrons was seen. Only when they changed the color
of the light (the wavelength) did they see a change in photoemission of electrons.
This was explained by Einstein using a theory that light consists of photons, each with
discrete quantum of energy proportional to their wavelength.
For an electron to be freed from the metal surface it would need a photon with enough energy
to overcome the energy that bound it to the atom. So, making the light brighter would supply
more photons, but none would have the energy to free the electron.
Light with a shorter wavelength consisted of higher energy photons that could supply the
needed energy to free the electron. Now, you ask, "What the heck does this idea of quantum
energy have to do with a laser?” Well, with this background under our belts we will
continue.

Chapter 6
Spectroscope of laser light
Line width:
In fact emission and absorption depend on photon frequency and are characterized by a line
width
Line broadening types include:
1. Natural, from finite lifetime (H)
2. Phonon, from lattice vibrations (H)
3. Collisional, in gases (H)
4. Strain, from static lattice in homogeneities (I)
5. Impurity ions in host crystal (I)
6. Doppler, in gases (I)
Line width Effects
A laser beam of intensity I (W/m2), propagating in the direction through a medium with gain
coefficient g (m-1) grows in intensity as I = I0 exp(gz) Since g depends on wavelength, this
process will increase the intensity for wavelengths near line-center faster than for those in the
wings, leading to gain-narrowing of the spectrum.
Line width properties
Atoms in either upper or lower levels of the laser medium will not interact with a perfectly
monochromatic beam. This is the fact that all spectral lines have a finite wavelength or
frequency spread, i.e., (fluorescent or spectral line width). This can be seen in both emission
and absorption,
And if we measured the emission of a typical spectral source as a function of frequency, we
will get bell-shaped curve illustrated. The precise shape of the curve is given by the line
shape function g(ν), which represents the frequency distribution of the radiation in a given
spectral line. The precise form of g(ν) which is normalized so that the area under the curve is
unity depends on the particular mechanism causing the spectral broadening.

Chapter 7
Applications of laser
The light beam produced by most lasers is pencil-sized, and maintains its size and direction
over very large distances; this sharply focused beam of coherent light is suitable for a wide
variety of applications. Lasers have been used in industry for cutting and boring metals and
other materials as well as welding and soldering, and for inspecting optical equipment. In
medicine, they have been used in surgical operations.
CDs and DVDs read and written to using lasers, and lasers also are employed in laser printers
and bar-code scanners. They are used in communications, both in fiber optics and in some
space and open-air communications; in a manner similar to radio transmission, the
transmitted light beam is modulated with a signal and is received and demodulated some
distance away. The field of holography is based on the fact that actual wave-front patterns,
captured in a photographic image of an object illuminated with laser light, can be
reconstructed to produce a three-dimensional image of the object.
Lasers have been used in a number of areas of scientific research, and have opened a new
field of scientific research, nonlinear optics, which is concerned with the study of such
phenomena as the frequency doubling of coherent light by certain crystals. One important
result of laser research is the development of lasers that can be tuned to emit light over a
range of frequencies, instead of producing light of only a single frequency. Lasers also have
been developed experimentally as weaponry.
Sophisticated laser system concepts are increasingly being used to address high bandwidth
free space optical (FSO) communications needs and for sensing applications.
.
Terrestrial and space based multi-mega/gigabit FSO links have been demonstrated but still
require advances in beam steering, detection schemes, adaptive optics and other methods of
mitigating atmospheric effects, and modulated laser encoding before wide applications are to
be realized. Optical sensors based on lasers are also progressing both in remote applications
as well as in on chip sensing, in communities ranging from environmental sensing to medical
diagnostics. Laser based sensing and free space communications both employ sophisticated
detection schemes. This meeting reports on the multiple applications of lasers in FSO
communications as well as in advanced sensing applications.

LASER BEAM MACHINING
Fig.7.1
Laser beam machining (LBM) is an unconventional machining process in which a beam of
highly coherent light called a laser is directed towards the work piece for machining. Since
the rays of a laser beam are monochromatic and parallel it can be focused to a very small
diameter and can produce energy as high as 100 MW of energy for a square millimeter of
area. It is especially suited to making accurately placed holes. It can be used to perform
precision micro-machining on all microelectronic substrates such as ceramic, silicon,
diamond, and graphite. Examples of microelectronic micro-machining include cutting,
scribing & drilling all substrates, trimming any hybrid resistors, patterning displays of glass

or plastic and trace cutting on semiconductor wafers and chips. A pulsed ruby laser is
normally used for developing a high power.
Fig.7.2
Extremely short pulses provide for minimal thermal damage to surroundings

Characteristics of Femtosecond Laser Micromachining
1. Very high peak powers in the range 1013W/cm2 provide for minimal thermal damage to
surroundings
2. Very clean cuts with high aspect ratios
3. Sub-micron feature resolution
4. Minimum redeposition
5. Possible to machine transparent materials like glass, sapphire etc.
ADVANTAGES:
1. Non-contact machining
2. Very high resolution, repeatability and aspect ratios
3. Localized heating, minimal redeposition
4. No pre/post processing of material
5. Wide range of materials: fragile, ultra-thin and highly reflective surfaces
6. Process can be fully automated.
Fig.7.3
INTENSITY DISTRIBUTION:
Fig.7.4
Focal length of 9mm FOCAL LENGTH OF 40mm Focal

Fig 7.5
APPLICATIONS IN MANUFACTURING
1. CLEANING
Emerging process, particularly driven by art and monument restoration (I.e. National
Museums and Galleries on Merseyside (NMGM) conservation centre
 Metal surfaces are well-suited for many laser cleaning applications. Optimized
beam settings will not metallurgically change or damage the laser treated
surface. Only the coating, residue or oxide targeted for removal is affected as the
laser beam is precisely adjusted not to react with the underlying metal surface.
 Laser beam power density is accurately and easily adjusted to achieve cleaning
results impossible with all other options.

Fig .7.6
2.ENGRAVING : Better “engraving” performance on metals Internal glass marking
Laser engraving, and laser marking, is the practice of using lasers to engrave or mark an object.
The technique does not involve the use of inks, nor does it involve tool bits which contact the
engraving surface and wear out. These properties distinguish laser engraving from alternative
engraving or marking technologies where inks or bit heads have to be replaced regularly
Fig.7.7
2. DRILLING: A high power pulsed Nd:YAG laser is normally used, occasionally a fiber
laser is chosen, or a CO2 laser can be used with non-metallic parts. Processing is
accomplished through either percussion drilling or trepanning. In the laser drilling

process, high power density is accomplished by using a high power laser and a focused
spot size of 0.05 mm (0.002") to 0.75 mm (0.030").
Fig.7.8
3. WELDING : Solid-state lasers operate at wavelengths on the order of 1 micrometer, much
shorter than gas lasers, and as a result require that operators wear special eyewear or use special
screens to prevent retina damage. Nd:YAG lasers can operate in both pulsed and continuous
mode, but the other types are limited to pulsed mode. The original and still popular solid-state
design is a single crystal shaped as a rod approximately 20 mm in diameter and 200 mm long, and
the ends are ground flat.
Fig.7.9
4. CUTTING: The parallel rays of coherent light from the laser source often fall in the range
between 0.06–0.08 inch (1.5–2.0 mm) in diameter. This beam is normally focused and intensified
by a lens or a mirror to a very small spot of about 0.001 inches (0.025 mm) to create a very

intense laser beam. In order to achieve the smoothest possible finish during contour cutting, the
direction of beam polarization must be rotated as it goes around the periphery of a contoured
workpiece. For sheet metal cutting, the focal length is usually 1.5–3 inches (38–76 mm)
Fig7.10
 Good edge quality (square ,clean and no burrs)
OTHER POPULAR LASER APPLICATIONS ARE
1. Spectroscopy
Most types of laser are an inherently pure source of light; they emit near-monochromatic
light with a very well defined range of wavelengths. By careful design of the
laser components, the purity of the laser light (measured as the "linewidth") can be improved
more than the purity of any other light source. This makes the laser a very useful source
for spectroscopy. The high intensity of light that can be achieved in a small, well collimated
beam can also be used to induce a nonlinear optical effect in a sample, which makes
techniques such as Raman spectroscopy possible. Other spectroscopic techniques based on
lasers can be used to make extremely sensitive detectors of various molecules, able to
measure molecular concentrations in the parts-per-1012 (ppt) level. Due to the high power

densities achievable by lasers, beam-induced atomic emission is possible: this technique is
termed Laser induced breakdown spectroscopy (LIBS).
Fig.7.11
2. Heat Treatment
Heat treating with lasers allows selective surface hardening against wear with little or no
distortion of the component. Because this eliminates much part reworking that is currently
done, the laser system's capital cost is recovered in a short time. An inert, absorbent coating
for laser heat treatment has also been developed that eliminates the fumes generated by
conventional paint coatings during the heat-treating process with CO2 laser beams.
One consideration crucial to the success of a heat treatment operation is control of the laser
beam irradiance on the part surface. The optimal irradiance distribution is driven by the
thermodynamics of the laser-material interaction and by the part geometry. Typically,
irradiances between 500-5000 W/cm^2 satisfy the thermodynamic constraints and allow the
rapid surface heating and minimal total heat input required. For general heat treatment, a
uniform square or rectangular beam is one of the best options. For some special applications
or applications where the heat treatment is done on an edge or corner of the part, it may be
better to have the irradiance decrease near the edge to prevent melting.
Fig.7.12

Lunar laser ranging
When the Apollo astronauts visited the moon, they planted retro reflector arrays to make
possible the Lunar Laser Ranging Experiment. Laser beams are focused through
large telescopes on Earth aimed toward the arrays, and the time taken for the beam to be
reflected back to Earth measured to determine the distance between the Earth and Moon with
high accuracy.
Photochemistry
Some laser systems, through the process of mode locking, can produce extremely brief pulses
of light - as short as picoseconds or femto seconds (10−12 - 10−15 seconds). Such pulses can be
used to initiate and analyses chemical reactions, a technique known as photo chemistry. The
short pulses can be used to probe the process of the reaction at a very high temporal
resolution, allowing the detection of short-lived intermediate molecules. This method is
particularly useful in biochemistry, where it is used to analyses details of protein folding and
function.
Fig7.13

Laser Barcode Scanners
Laser barcode scanners are ideal for applications that require high speed reading of linear
codes or stacked symbols. From small products for embedded OEM applications to rugged
laser barcode scanners for industrial use, Micro scan offers a wide range of quality products
to read linear barcodes and stacked symbols, with features such as high speed reading, wide
field of view, symbol reconstruction, and aggressive decoding technology.
Fig7.14
Laser cooling
A technique that has recent success is laser cooling. This involves atom trapping, a method
where a number of atoms are confined in a specially shaped arrangement
of electric and magnetic fields. Shining particular wavelengths of laser light at the ions or
atoms slows them down, thus cooling them. As this process is continued, they all are slowed
and have the same energy level, forming an unusual arrangement of matter known as a Bose-
Einstein condensate.
Fig .7.15

Nuclear fusion
Some of the world's most powerful and complex arrangements of multiple lasers and optical
amplifiers are used to produce extremely high intensity pulses of light of extremely short
duration. These pulses are arranged such that they impact pellets of tritium-deuterium
simultaneously from all directions, hoping that the squeezing effect of the impacts will
induce atomic fusion in the pellets. This technique, known as "inertial confinement fusion",
so far has not been able to achieve "breakeven", that is, so far the fusion reaction generates
less power than is used to power the lasers, but research continues.
Fig7.16
Microscopy
Confocal laser scanning microscopy and Two-photon excitation microscopy make use of lasers to
obtain blur-free images of thick specimens at various depths. Laser capture microdissection use
lasers to procure specific cell populations from a tissue section under microscopic visualization.
Additional laser microscopy techniques include harmonic microscopy, four-wave mixing microscopy
and interferometric microscopy.

Fig.7.17

Working:
A laser printer is a popular type of personal computer printer that uses a non-impact (keys
don't strike the paper), photocopier technology. When a document is sent to the printer, a
laser beam "draws" the document on a selenium-coated drum using electrical charges. After
the drum is charged, it is rolled in toner, a dry powder type of ink. The toner adheres to the
charged image on the drum. The toner is transferred onto a piece of paper and fused to the
paper with heat and pressure. After the document is printed, the electrical charge is
removed from the drum and the excess toner is collected. Most laser printers print only in
monochrome. A color laser printer is up to 10 times more expensive than a monochrome
laser printer
SKIN TREATMENT
.
Fig.7.18
If you have fine lines or wrinkles around your eyes or mouth or on your forehead, shallow scars from
acne, or non-responsive skin after a facelift, then you may be a good candidate for laser skin
resurfacing.

The two types of lasers most commonly used in laser resurfacing are carbon dioxide (CO2) and
erbium. Each laser vaporizes skin cells damaged at the surface-level.
The newest version of CO2 laser resurfacing uses very short pulsed light energy (known as
ultrapulse) or continuous light beams that are delivered in a scanning pattern to remove thin layers
of skin with minimal heat damage. Recovery takes up to two weeks.
Fig.7.19

FUTURE DEVELOPMENT
Ignition of fuel through laser beam
A method for igniting a fuel mixture in an internal combustion engine,
1. The method comprising: Generating a laser beam.
2. Transmitting the laser beam through a lens to form a focused laser beam. and
3. Transmitting the focused laser beam through a prism to focus the laser beam on the fuel
mixture supplied into a combustion chamber of the internal combustion engine, wherein
the lens moves linearly to transmit the laser beam.
Fig.7.20

Anti-Missile Defence System
Fig7.21
Current missile defenses consist of missiles fired at other missiles. If Lockheed
Martin has its way, that may change in a few years, with missiles being shot down
by laser beams
The advantage of laser-based defense over missile-based is that tracking is less
complex. Missiles need to calculate trajectories and even be able to maneuver (as
with Iron Dome) toward their target. Lasers do not. Plus, a laser beam moves at the
speed of light, so at a range of a mile, it can hit its target in less than five-millionths
of a second. Lastly, laser weapons cost less to fire, since they aren’t using up real
ammunition, jut power.

Chapter 8
The Future of the Laser
Modern technology is advancing so quickly that the average person simply cannot keep up with it.
Even some scientists are occasionally unaware of discoveries being made in other fields. Lasers are
very much a part of this technology explosion. They help in the discovery of new knowledge, which
further fuels the explosion while, by advancing communications, they help spread the new
knowledge to those who want it.
Realistic Images in Homes and Offices
Many experts expect laser-computer advances to lead to the eventual perfection of holography,. It
will be like watching old-fashioned 3D movies, only without the special glasses. Even holographic
television will likely be developed, although it will be very difficult to construct because so much
information is needed to form a holographic image. To transmit the information of a single
hologram to a home, it will take a cable with the capacity of five hundred television channels. Once
the hologram arrives in someone's living room, the television itself will have to be able to project
the hologram, and this will require a screen with more than one thousand times more detail than
today's TV screens.
Computing at Light Speed
In the mid-1990s the laser joined in a useful working partnership with the computer, but the laser
still only reads, writes, and memorizes for the computer. Some scientists think the laser could go
further and bring about a drastic change in the way the computer is designed. The computer itself
consists of wires, chips, connections, and other parts through which electrical signals flow. Experts
point out that in the larger supercomputers sometimes too many pieces of information try to get to
the same place at the same time.
Walking Electronics Stores?
Advanced laser-based devices may also transform ordinary people into virtual walking electronics
stores. The fact that the beam of a laser can be focused to a microscopic point has already given it
the ability to create discs to store vast amounts of information, including video and audio discs of
high quality. Researchers are now working to expand this principle to the miniaturization of
electronic devices so that they can be carried or even worn by the average person.
Lasers and Nuclear Fusion
Most nuclear scientists believe that in the future nuclear power will be supplied by fusion, a nuclear
reaction in which two atoms are combined. But starting a fusion reaction requires an enormous
initial force. Many scientists think that "laser chains" can supply that force. A laser chain consists of
several laser amplifiers over a hundred feet long, which intensify the power of laser beams. The
high-powered beams are directed through beam splitters and onto mirrors so that several beams
strike a tiny fuel pellet from all sides at once. This causes an explosion powerful enough to trigger a
fusion reaction. The laser may provide a way to get a safe fusion reaction going. Experiments with
lasers and fusion began in the late 1960s, but progress was slow for a long time. A major

breakthrough occurred in August 2001 when researchers from Japan and the United Kingdom
succeeded in using a laser beam to compress a ball -like
Fig8.1
Twenty-four lasers are arranged for a nuclear fusion experiment. Controlled fusion has not yet been
perfected, but lasers may open the door to that important new technology.
A World Transformed.
In the twenty-first century and beyond, the laser promises to help raise human civilization to new
heights. The supertool will build a storehouse of knowledge and put that knowledge within easy
reach of most people. Laser light will illuminate a complex and computerized world, one in which
technology allows men and women to live increasingly productive and happy lives. Indeed, the laser
may one day harness the fire of the stars to give humanity clean, safe, and abundant energy for
generations to come as well as access to alien knowledge that could transform the world in ways not
yet imagined.

REFERENCES
1. http://lasers.coherent.com/lasers/laser%20application%20in%20engineering%20field
2. http://en.wikipedia.org/wiki/Medical_imaging
3. http://en.wikipedia.org/wiki/Laser_printing
4. http://www.scienceclarified.com/scitech/Lasers/The-Future-of-the-Laser.html
5. http://www.howstuffworks.com/laser.htm
6. http://en.wikipedia.org/wiki/Laser_engraving
7. http://en.wikipedia.org/wiki/Laser_beam_machining
8. www.sciencedirect.com/science/article
9. drdo.gov.in/drdo/data/Laser%20and%20its%20Applications.
10. hyperphysics.phy-astr.gsu.edu/hbase/optmod/lasapp.html
11. www.google.com/images/heat treatment
12. www.google.com/images/ microscopy
13. www.google.com/images/ WELDING

APPENDIX
Page no.
1. Fig.1.1 Laser light 1
2. Fig.1.2-Fig1.3 Properties of light 2
3. Fig 2.1 Scientist who developed laser 3
4. Fig. 2.2 Laser research center 7
5. Fig.3.1 Components of laser 8
6. Fig.4.1-Fig4.8 Types of laser 11-16
7. Fig 5.1 Albert Einstein 17
8. Fig 5.2 Working of laser 18
9. Fig.7.1-Fig7.21 Applications of laser 21-36
10. Fig8.1 Lasers and Nuclear Fusion 38

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