This PPT has covered, 1)Principle of Laser 2) Types of Laser 3)Application Of Laser

2.  Outline:-
 Introduction
 Basic processes
 Types of Laser
Ruby Laser
He-Ne Laser
 Application of LASER

3. LASER
An acronym LASER is used for Light Amplification by Stimulated
Emission of Radiation.
Due to some unique properties laser beam is superior as compared to
other light sources.
 Highly Monochromatic
 Highly Directional
 Coherence
 High intense
Characteristics of LASER

4. Stimulated Absorption
If the photon of energy ℎ𝜈 is incident on the atom in the lower
energy state, the atom absorbs the incident photon and gets excited, to
higher energy state.
Atom + Photon = Atom*

5. Spontaneous Emission
Atom in the excited state makes transition from high energy state
to lower energy state through the emission of photon with energy ℎ𝜈.
Atom* = Atom + Photon

6. Stimulated Emission
If the photon of energy ℎ𝜈 is incident on the atom in the higher energy
state, the atom absorbs the incident photon and gets excited, from higher energy
state to lower energy state with the emission of photon of energy 2ℎ𝜈.
Atom* + Photon = Atom + 2 ℎ𝜈

7. Metastable State
Pumping
Metastable state is basically an
intermediate state between ground state and
excited state. The lifetime of metastable state is
about 10−3
𝑆𝑒𝑐.
Metastable state helps to achieve
state of population inversion in laser system.
The mechanism or process of raising an atom from ground state
to higher energy state is known as pumping.

8. Ruby Laser
Schematic of Ruby laser

9. Construction of Ruby Laser
It mainly consist of 3 components
1. Active Material : It is a solid state laser, in which a rod of a synthetic ruby crystal is
used as an active medium. A ruby crystal is obtained by doping a small amount of
chromium oxide (0.05%)(C𝑟2𝑜3) in aluminum oxide 𝐴𝑙2𝑜3 . This chromium ion gives
the crystal pink or red color depending upon doping concentration. The length of the
ruby rod is usually 2cm to 30cm and the diameter is 0.5cm to 2cm.
2. Pumping Source : The ruby rod is placed inside a helically shaped xenon flash lamp to
excite the 𝐶𝑟3+ion. Thus in ruby laser population inversion is achieved by using optical
pumping.
3. Resonator Cavity : the end of the ruby rod are polished such that they becomes flat
and parallel to each other. Now one of the end is coated with silver completely while the
other is partially silvered. Thus, the two silver coated end of the rod acts as an optical
resonator system.

10. Working of Ruby Laser

11. Ruby laser is three energy level laser system. After absorbing light
photon of wavelength 5500 𝐴0 from xenon lamp, some of the chromium ions at the
ground state 𝐸1 gets excited to higher energy state 𝐸3.
At this state they are unstable and by losing a part of energy to crystal
lattice, they fall to metastable state and population inversion is occur between 𝐸2
and 𝐸1.
Now some of the 𝐶𝑟3+ ion will decay spontaneously to ground state by
emitting photon of wavelength 694.3𝑛𝑚. The photons that are moving parallel to
axis of the rod will reflect back and forth by the silvered end of the rod and
stimulates other excited 𝐶𝑟3+ ions to radiate another photon with the same phase.
Thus due to successive reflections of these photons at the end of the rod,
the number of photons multiplies. After few microseconds, a monochromatic ,
intense and collimated beam of red light of wavelength 694.3𝑛𝑚 emerges through
the partially silvered end of the rod.

12. He-Ne Laser
Schematic of He-Ne laser

13. Construction of He-Ne Laser
It mainly consist of 3 components
1. Active Material : It is a gas laser, which consist of a narrow quartz tube filled with
a mixture of helium and neon gases in the ratio of 10:1 respectively. Ne atom acts
as a active centers and responsible for the laser action, while He atoms are used to
help in the excitation process.
2. Pumping Source : The pumping is done through electrical discharge by using
electrode that are connected to high frequency alternating current source.
3. Resonator Cavity : To construct the optical resonator cavity, two parallel mirrors
are placed at the end of the quartz tube one of them is partly transparent while
other is fully reflecting

14. Working : It is a four energy level laser system. The electron produced from electric
charge collide with the helium and neon atom and excite them to higher energy level 𝐻𝑒2
to 𝑁𝑒4. these two states are metastable state so atom may stay there for longer time. They
are very close to each other, thus some of the He atoms at 𝐻𝑒2 state may transfer the
energy to the ground state 𝑁𝑒 atom through collision and excite them to higher energy
level. The kinetic energy of atom provide the additional energy of 0.05eV. Thus He atoms
helps to achieve population inversion in Ne atoms. Now some of the neon atom decay
spontaneously to lower energy state by emitting a photon of wavelength 632.8nm. The
photons that are moving parallel to axis of tube will reflect back and forth by the end
mirrors of the rod and stimulate other excited Ne atom to radiate another Photon of the
same phase. Thus due to success your reflection of these Photons at the end of the tube,
the number of photons multiplies. after a few micro seconds, a monochromatic, intense
collimated beam of red light of wavelength of 632.8nm emerges through the partially
silvered mirror. The atoms in 𝑁𝑒3 are unstable and decay spontaneously to lower state
𝑁𝑒2 and finally they come to ground state by losing their remaining energy through
collision with the wall of tube. He- Ne laser operates continuously.

15. Application of Laser
In medicine :
 To break kidney stone
 To weld broken tissue (e.g. detached retina)
 To destroy cancerous and precancerous cells
 To remove mole, tattoo
 Used to measure blood cell diameter
 Can also used for dental treatment
In industry :
 Lasers are used cutting,
drilling, welding, cladding,
soldering etc.

16. In communication :
 As laser has large bandwidth, more
amount of data can be sent.
 More channels can be simultaneously
transmitted.
In Military :
 Laser can serve as a war weapon.
 High energy lasers are being employed to
destroy enemy air crafts and missiles.
 Laser beam can be bounced off a target
such as enemy air plane or ship, to
determine its distance and speed.

17. Thank you…!!!!