Light Amplification by Stimulated Emission of Radiation. Its basic principle of working, features or characteristics, types, applications, hazards caused by LASER and future scopes.

1. “LASER”

2. 2
Contents
Serial no. Topic Slide no.
1. Introduction 3
2. Principle involved in working of a Laser 4-5
3. Construction of Laser 6-8
4. How does laser work? 9-11
5. Characteristics of Laser light 12
6. Features of Laser 13
7. Types of Laser 14
8. Applications of Laser 15
9. Hazards caused by Laser 16
10. Future scopes of Laser 17
11. Leading suppliers of Laser 18
12. References 19

3. Introduction
 “LASER” is an acronym for “Light Amplification by Stimulated Emission of
Radiation”.
 The first laser was built in 1960 by Theodore H. Maiman at Hughes Research
Laboratories.
 It generates an intense beam of coherent monochromatic light through a
process called stimulated emission of radiation which amplifies or increases the
intensity of light.
3

4. Principles involved in working of a Laser
In lasers, photons are interacted in three
ways with the atoms:
 Absorption of radiation
 Spontaneous emission
 Stimulated emission
 Absorption of radiation: Absorption
of radiation is the process by which
electrons in the ground state
absorbs energy from photons to jump
into the higher energy level.
4

5.  Spontaneous emission: Spontaneous
emission is the process by which
electrons in the excited state return to the
ground state by emitting photons.
 Stimulated emission: Stimulated
emission is the process by which incident
photon interacts with the excited electron
and forces it to return to the ground state.
5

6. A laser or laser system consists of three
components: The Excitation Mechanism or
Energy Pump, The Laser Medium, and The
Optical Cavity.
1. The Excitation Mechanism or Energy
Pump: The excitation mechanism of a laser
is the source of energy used to excite the
lasing medium. Excitation mechanisms
typically used are: electricity from a power
supply, flash tubes, lamps, or the energy
from another laser.
6
Construction of Laser
Flash tube

7. 2. The Laser Medium: The laser
medium is a medium where
spontaneous and stimulated
emission of radiation takes place. It
determines the characteristics of
the laser light emitted. The laser
medium can be solid, liquid, or
gaseous.
7

8. 3. The Optical Cavity: The laser medium is
surrounded by two parallel mirrors which
provides feedback of the light. One mirror
is fully reflective (is called High reflector)
whereas the partially reflective (is called
Output coupler). These two mirrors as a
whole is called optical resonator, which is
also known as optical cavity or resonating
cavity. The output coupler will allows
some of the light to leave the optical
cavity to produce the laser’s output
beam.
8
Optical resonator

9. How does laser work?
 Energy is supplied to the laser medium by the energy pumping system. Pumping must
produce a population inversion before laser action can take place.
 When population inversion is achieved, the spontaneous decay of a few electrons from
the meta stable energy level to a lower energy level starts a chain reaction.
 The photons emitted spontaneously will hit other atoms and stimulate their electrons to
make the transition from the meta stable energy level to lower energy levels- emitting
photons of precisely the same wavelength, phase, and direction. This action occurs in
the optical cavity.
 When the photons that decay in the direction of the mirrors reach the end of the laser
material, they are reflected back into the material where the chain reaction continues
and the number of photons increase. When the photons arrive at the partially-
reflecting mirror, only a portion will be reflected back into the cavity and the rest will
emerge as a laser beam.
9

10. 10
Fig: Basic Laser Operation
Population inversion:
Population inversion is the
process of achieving
greater population of
higher energy state as
compared to the lower
energy state. This
technique is mainly used
for light amplification and
is required for laser
operation.

11. 11

12. Characteristics of Laser light
Laser light has following unique characteristics that differentiates it from ordinary
light:
a) Monochromatic: The light emitted from a laser is monochromatic, that is, it is of
one wavelength (color). In contrast, ordinary white light is a combination of many
different wavelengths (colors).
b) Coherent: The light from a laser is said to be coherent, which means the
wavelengths of the laser light are in phase in space and time.
c) Directional: Laser light is emitted as a relatively narrow beam in a specific
direction so is highly directional whereas ordinary light, such as coming from the
sun, a light bulb, or a candle, is emitted in many directions away from the source.
d) Intensity: In case of laser, due to high directionality, the intensity of laser beam
reaching the target is of high intense beam.
12

13. Features of Laser
Laser light has the following special features or properties:
 It is usually emitted as a laser beam which can propagate over long
lengths without much divergence and can be focused to very small
spots.
 It can have a very narrow optical bandwidth, whereas e.g. most
lamps emit light with a very broad optical spectrum.
 It can be emitted continuously, or alternatively in the form of short or
ultra-short pulses with durations from microseconds(10-6) down to a
few femtoseconds(10-15).
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14. Types of Laser
Lasers are classified based on the type of laser medium used, namely:
 Solid state lasers- E.g.: Ruby or neodymium-YAG (Yttrium Aluminum Garnet)
lasers.
 Gas lasers- E.g.: Helium(He) and Helium-Neon(HeNe) lasers, CO2 lasers etc.
 Dye lasers- These lasers use complex organic dyes like Rhodamine 6G in
liquid solution or suspension as lasing media. They are tunable over a broad
range of wavelengths.
 Semiconductor lasers- These are sometimes called diode lasers. These
electronic devices are generally very small and use low power and may be
built into larger arrays, e.g., the writing source in some laser printers or
compact disk players.
14

15.  Lasers in medicine- used to destroy kidney stones, cancer diagnosis and therapy, in
fiber-optic endoscope to detect ulcers in the intestines, for eye lens curvature
corrections etc.
 Lasers in communications- used in optical fiber communications to send
information over large distances with low loss, space communication, radars and
satellites etc.
 Lasers in industries- used to cut glass and quartz, in electronic industries for
trimming the components of Integrated Circuits (ICs), in the semiconductor industries
for photolithography etc.
 Lasers in science and technology- used to store large amount of information or
data in CD-ROM, in determining the rate of rotation of the earth accurately, in
computer printers etc.
 Lasers in military- used in LIDAR’s to accurately measure the distance to an object,
to dispose the energy of a warhead by damaging the missile etc.
15
Applications of Laser

16.  Improperly used laser devices are potentially dangerous. Effects can
range from mild skin burns to irreversible injury to the skin and eye.
 Acoustical effects result from a mechanical shockwave, propagated
through tissue, ultimately damaging the tissue.
 Some non-beam hazards include Electrical hazards, Mechanical
hazards, Explosion hazard, Compressed gases, Laser dyes and
solvents, Laser generated air contaminants, X-Ray radiation, Radio
Frequency radiation etc.
16
Hazards caused by Laser

17.  An area of research in which lasers have made a big impact is
nanotechnology - the development of super-tiny machines and tools.
 As laser light can be controlled very precisely, so scientists can use it to
perform extremely fine operations. For example, lasers could be used to
cut out parts to make molecule-size motors.
 Lasers can also be used as “optical tweezers” to handle extremely small
objects such as molecules.
 Scientists are even beginning to use lasers to change the shape of
molecules by varying the laser’s wavelength.
17
Future scopes of Laser

18.  Lasers have developed greatly in their variability and application since
Einstein’s theoretical ideas and the first use of a laser by Theodor
Maiman at the end of the 1950s.
 In terms of future innovation, laser use has the potential to be developed
in regard to new wavelength bands, improvement in the average output
power, peak pulse energy and power levels, as well as improvements in
cost, power, and size efficiency.
 These parameters will help medicine use lasers across a wider breadth
of specialties with simpler, cheaper and smaller laser applications
allowing a wider acceptance of laser use and introduction to smaller
hospital units.
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Conclusion

19. 19
Leading suppliers of Laser

20. References
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1. https://toutestquantique.fr/en/laser/
2. https://www.physics-and-radio-electronics.com/physics/laser/
3. https://en.wikipedia.org/wiki/Laser
4. https://www.rp-photonics.com/lasers.html
5. https://ehs.oregonstate.edu/laser/
6. https://www.ulsinc.com/learn