LASER and its applications document is summarized as follows: 1. LASER (Light Amplification by Stimulated Emission of Radiation) was first conceptualized by Einstein and later developed by Townes, Schawlow, and Maiman. A laser produces coherent, monochromatic light through stimulated emission in an active medium within an optical cavity. 2. Key laser components include the active medium which contains energy levels that can absorb or emit radiation, pumping to create population inversion, and an optical resonator. 3. Lasers have properties like coherence, monochromaticity, directionality, and high brightness that make them useful for applications in medicine, industry, science, and military such

1. LASER And Its
Application
Abdul Ahad Hadi
M Rizwan Rizvi
Sania Arshad
Urooj Fatima

2. History
MASER
Micro-wave Amplification by Stimulated Emission of Radiation
In 1917 Albert Einstein gave the idea of Stimulated Emission of Radiation.
Charels H. Townes Inventor of MASER.
He thought that molecules in the excited state could be stimulated to emit
microwaves when placed in cavity.
With the help of his fellows and students he invented a working MASER in 1953.
He ,with his team, awarded Nobel Prize in Physics in 1964.
Townes began looking beyond the microwave region to shorter wavelength.

3. LASER
It was Gordon Gould who first used the word LASER in his research papers.
In the mid of 1960, Theodore H. Maiman, demonstrated first LASER.
A laser is a device that emits light through a process of optical amplification based on
the stimulated emission of electromagnetic radiation.
 LASER: light amplification by stimulated emission of radiation

4. L Light (not visible only) it also ranges upto x-rays
A Amplification (not to increase the amplitude but intensity)
S Stimulated
E Emission
R Radiation

5. Difference between
Spontaneous and Stimulated Emission
 Spontaneous emission: Electron drops from an excited state to a lower state (no
outside mechanism) - emitting a photon.
 Stimulated emission (lasers): Stimulated emission is the process by which an
atomic electron (or an excited molecular state) interacting with an electromagnetic
wave of a certain frequency may drop to a lower energy level, transferring its
energy to that field. A new photon created in this manner has the same phase,
frequency, polarization, and direction of travel as the photons of the incident
wave.
 This is in contrast to spontaneous emission which occurs without regard to the
ambient electromagnetic field.

6. Emission of Radiations

9. Basic Principle Of LASER
 Active Medium
 LASER Pumping
 Optical Resonator

10. Active Medium
The heart of a laser system is a material capable of emitting radiation of the required
energy. This material, known as active medium, may have any form e.g. solid, liquid,
or gas but must contain a set of energy levels in which it can absorb or emit energy in
the form of optical radiation.
1. Energy Levels
2. Transitions
3. Spontaneous Emission
4. Stimulated Emission
5. Absorption

11. LASER Pumping
The population inversion required for light amplification constitutes an abnormal
distribution of atoms among the various available energy levels. To understand how
light amplification can be achieved in a medium, it is necessary to consider the
Boltzmann distribution and then pumping mechanism to achieve the population
inversion.
Population Inversion
The population inversion condition required for light amplification is a non-equilibrium
distribution of atoms among the various energy levels of the atomic system. If the energy
difference between E1 and E2 is nearly equal to kT (~0.025 eV at room temperature) then the
population of the upper level would be 1/e or r 0.37 times of the lower level. For an energy
difference large enough to give visible radiation (~2.0 eV), however, the population of the
upper level is almost negligible.

12. Four Level Pumping
For the analysis of steady-state laser pumping and
population, we consider a neodymium laser which is a
typical example of four-level laser system. The
complicated energy levels of Nd+3 have been
simplified into the idealized four-level laser system
shown in Figure. This four-level model will in fact
provide a simple but surprisingly accurate analytical
model for many laser systems

13. Three Level Pumping
A three-level system differs from the four-level
system in that the lower laser level is the ground
level E1. This is a serious disadvantage, since
more than half the atoms initially in the ground
state must be pumped through the upper
pumping level E3 into the upper laser level E2
before any inversion at all is obtained on the 2
1 transition. Three-level lasers are, therefore,
usually not as efficient as four-level lasers.

14. Optical Resonator
A typical optical resonator formed by two curved
mirrors with radii of curvature R1 and R2 spaced a
distance L apart is shown in Figure. For each mirrors R
> 0 implies that the mirror is concave towards the
resonator

15. From this similarity (between a curved mirror and a thin
lens) we can deduce that the behaviour of a ray upon
repeated bounces back and forth between these two mirrors
will be exactly the same as the behaviour of a ray passing
through a series of lenses spaced at intervals L, with alternate
focal lengths f1 = R1/2 and f2 = R2/2.

16. LASER
Components

17. LASER Beam Properties
 MonoChromatic
 Coherent
 Directionality
 Brightness
 Focusing Property

18. Monochromatic
The word monochromatic is derived from Greek language, meaning
single color. In the scientific world it is used for electromagnetic waves
of single frequency. In fact no light source, including laser, is capable
of producing absolutely monochromatic light, we can only make better
and better approximations to the ideal. We might begin with a white
light source that produces light of all colors of the spectrum, and filter
it with a piece of colored glass. The monochromaticity of the filtered
light is now as good as the filter. If the radiation from a gas discharge
source, such as neon sign or a sodium vapor lamp, is directed through a
prism, a series of lines of different colors is seen on a screen.

19. Coherent
 Coherence probably is the best-known
property of laser light. Light waves
are coherent if they are in phase with
each other, i.e., if their peaks and
valleys are lined up at the same point.
Two things are necessary for light
waves to be coherent. First, the light
waves must start out having the same
phase at the same position. Second,
their wavelengths must be the same,
or they will drift out of phase because
the peaks of the peaks of the longer
wave.

20. Directionality
 We think of laser beams as tightly focused and straight, but once they go for
enough from the laser, they actually spread out slightly with distance. The
spreading is called beam divergence. Laser beams, in general, have very low
divergence.
Brightness
 The primary characteristic of laser radiation is that lasers have a higher brightness
than any other light sources. We define brightness as power emitted per unit area
per unit solid angle. The relevant solid angle is that defined by the cone into
which the beam spreads. Hence, as lasers can produce high levels of power in
well-collimated beams, they represent sources of great brightness.
 The brightness of Sun is ~ 1.3x106 W m-2 sr-1 .

21. Focusing Property
 The minimum spot size to which a laser beam can be focused is
determined by diffraction. A single mode beam can be focused into a
spot, which has dimensions of the order of the wavelength of light.
The imperfections in the optical system may mean that we cannot
achieve this in practice. A useful relation for estimating the spot size
is that the radius r, at the focal plane of a lens of focal length f is
given by
r = f.ϴ

22. Applications of LASER
 Laser light is different from an ordinary light. It has various unique properties
such as coherence, monochromacity, directionality, and high intensity. Because of
these unique properties, lasers are used in various applications.
The most significant applications of lasers include:
1. Lasers in medicine
2. Lasers in industries
3. Lasers in science and technology
4. Lasers in military

24. Removal of Tissue by Laser Surgery
Laser has very high intensity (power/area) and can produce
intense heat on a specific spot. Today most laser surgery makes
use of this heat primarily because its destructive effects can be
extremely selective and precisely controlled. To have an idea
about the removal of tissue using lasers, one must know that
how laser light interacts with the tissue. Tissue like any other
material absorbs light differently at different wavelengths. If
the wavelength of a laser is matched very closely with the
absorption band of the target structure; the laser light will be
absorbed by and therefore damage that structure.

25. LASER In Dermatology
Dermatology is the medical field concerned with diseases of the skin. Laser has given
dermatologists an improved new tool to treat some conditions. This technology was
easily introduced in dermatological therapeutic because dermatologists have long
been used ordinary light for skin treatments.
Lasers can be used to treat port-wine stains, tattoos, seborrhea, warty keratoses, basal
cell carcinomas, warts, freckles, nevi, acne and various growths both benign and
malignant. Generally the laser is used to remove some sort of growth or colored area
in the skin and in general the results are comparable to conventional modes of
therapy.

26. Treatment of Port-Wine Stains
Dark-red birthmarks called port-
wine stains often appear on the
face or neck. Networks of
abnormal blood vessels just under
the surface of the skin cause port-
wine stains as shown in Figure
9.12. Because port-wine stains are
dispersed on the surface of the
skin, conventional surgery can't
remove them effectively. Laser can
treat this condition

27. Shattering of the Stones
Delivery of light from a dye laser through optical fiber can shatter kidney stones and
gall stones into pieces small enough to pass freely from the body. The laser is tuned to
a wavelength strongly absorbed by the stones. Prospects for this treatment look very
good.

28. Cancer Treatment
 Lasers are an integral part of a new
treatment for cancer called
photodynamic therapy. Scientists
noted that cancerous tissue
concentrated some of the body's own
pigments, particularly porphyrin, in
the brownish-red pigment of blood.
The treatment relies on a dye, called
hematopophyrin derivative (HpD)
which cancer cells retain much longer
then healthy cells.

29. Treatment of Detached Retina
Figure shows the structure of the
human eye. Retina is the light
sensitive layer at the back of the
eye. Sometimes the retina can
become torn and detached from
the back of the eyeball.

30. The damage can spread, and without
treatment the entire retina can come
loose from the back of the eye
causing blindness. A laser pulse
focused on the retina can stop the
detachment from the eyeball. An
instrument that has the opportunity of
working closer to the macula is
shown

31. LASER In Industry And Commercial
Levelling of ceramic
tiles floor with a
laser device

32. Lasers used for
visual effects
during a
musical
performance.

36. Bird Deterrent
Laser beams are used to disperse birds from agricultural
land, industrial sites, rooftops and from airport runways.
Birds tend to perceive the laser beam as a physical stick.
By moving the laser beam towards the birds, they get
scared and fly away.

37. LASER In
Military

40. References
 Gould, R. Gordon (1959). "The LASER, Light Amplification by
Stimulated Emission of Radiation". In Franken, P.A.; Sands R.H. (Eds.).
The Ann Arbor Conference on Optical Pumping, the University of
Michigan, 15 June through 18 June 1959. p. 128. OCLC 02460155.
 "laser". Reference.com. Retrieved May 15, 2008.
 "Four Lasers Over Paranal". www.eso.org. European Southern
Observatory. Retrieved 9 May 2016.
 Conceptual physics, Paul Hewitt, 2002
 "Schawlow and Townes invent the laser". Lucent Technologies. 1998.
Archived from the original on October 17, 2006. Retrieved October 24,
2006.
 Chu, Steven; Townes, Charles (2003). "Arthur Schawlow". In Edward P.
Lazear (ed.),. Biographical Memoirs. vol. 83. National Academy of
Sciences. p. 202. ISBN 0-309-08699-X
 Laser and optics
 Habiba Arain (laser and its applications) www.slideshare.net