TYPES OF LASERS THEIR WORKING AND APPLICATIONS

1. ACTIVE LEARNING ASSIGHMENT ON
TYPES OF LASER AND ITS APPLICATIONS
PRESENTED BY FACULTY
BHARGAV DESAI – 035
PRUTHVIGABANI -
PARTH CHOVATIA-
BATCH A2
DEPERTMENT-CE
GANDHINAGAR INSTITUTE OF TECHNOLOGY

2. LASER
L
A
S
E
R
ight
mplification by
timulated
mission of
adiation

3. TYPES OF LASERS
•Solid State Lasers
•Gaseous state Lasers
•Dye Lasers
•Semiconductors Lasers

4. Main Working of Lasers
 A Laser covers mainly below given points:
 Population Inversion
 Pumping
 Direct Conversion
 Lasing
 LifeTime
 Metastable State
 Active Medium
 Optical Resonator

5. Different Types of Lasers
Solid State Lasers Gaseous state Lasers
 Ruby Lasers
 Ne- He Laser
Semi conductors Lasers
 Ga-As Laser

6. Active Medium:
•The active laser medium (laser gain/amplification medium) is a
synthetic ruby rod.
•Ruby is an aluminum oxide crystal in which some of the aluminum
atoms have been replaced with chromium atoms(0.05% by weight).
•Chromium gives ruby its characteristic red color and is responsible
for the lasing behavior of the crystal.
•Chromium atoms absorb green and blue light and emit or reflect only
red light. For a ruby laser, a crystal of ruby is formed into a cylinder.
Resonator Cavity : A resonator cavity is made of flash tube like
solenoid with a ruby rod in the centre , both the side mirrors one
partial reflecting mirror and other fully.
1. RUBY LASER

7. OPTICAL PUMPING:
A xenon lamp is rolled over ruby rod and is used for
pumping ions to excited state.
RUBY LASER (WORKING)
WORKING:
Ruby laser is based
on three energy
levels.The upper
energy level E3 I
short-lived, E1 is
ground state, E2 is
mate stable state
with lifetime of
0.003 sec.

8. RUBY LASER ( WORKING ).
The ions after giving a
part of their energy to
crystal lattice decay to
E2 state undergoing
radiation less transition.
In meta stable state , the
concentration of ions
increases
while that of E1
decreases. Hence ,
population inversion is
achieved.
Meta stable state

9. Application
 Ruby lasers have declined in use with the discovery
of better lasing media. They are still used in a
number of applications where short pulses of red
light are required. Holography around the world
produce holographic portraits with ruby lasers, in
sizes up to a meter squared.
 Many non-destructive testing labs use ruby lasers to
create holograms of large objects such as aircraft
tires to look for weaknesses in the lining.
 Ruby lasers were used extensively in tattoo and hair
removal

10. ACTIVE MEDIUM:
The gain medium of the laser, as suggested by its name, is a mixture of helium
and neon gases, in a 5:1 to 20:1 ratio, contained at low pressure (an average 50 Pa
per cm of cavity length ) in a glass envelope.
PUMPING:
The energy or pump source of the laser is provided by an electrical discharge of
around 1000 volts through an anode and cathode at each end of the glass tube. A
current of 5 to 100 mA is typical for CW operation.
OPTICAL PUMPING:
The optical cavity of the laser typically consists of a plane, high-reflecting mirror
at one end of the laser tube, and a concave output coupler mirror of
approximately 1% transmission at the other end.
2.He-Ne Laser ( Helium Neon)

11. CONSTRUCTION:
Here helium and neon gas in appropriate amount is taken in the
glass type of cavity, here on both opening there are mirrors ,one
of fully reflecting and other partially. Inside the cavity one end is
connected with the cathode and other with the anode,futher
Connected with the AC supply.
He-Ne Laser (construction).

12. WORKING:
•When the power is switched on, An energetic electron collision
excites a He atom to the stable state.
• The excited He*(21 S) atom collides with an unexcited Ne atom and
the atoms exchange its internal energy, with an unexcited Ne atom
and excited He atom. This energy exchange process occurs with high
probability only because of the accidental near equality of the two
excitation energies of the two levels in these atoms. Thus, the
purpose of population inversion is fulfilled.
•When the excited Ne atom passes from meta stable state(3s) to
lower level(2p), it emits photon of wavelength 632 nm.
He-Ne LASER ( Working ).

13. •This photon travels through the gas mixture
parallel to the axis of tube, it is reflected back
and forth by the mirror ends until it stimulates
an excited Ne atom and causes it to emit a
photon of 632nm with the stimulating photon.
•The stimulated transition from (3s) level to
(2p) level is laser transition.
•This process is continued and when a beam of
coherent radiation becomes sufficiently strong,
a portion of it escape through partially silvered
end.
•The Ne atom passes to lower level 1s emitting
spontaneous emission. and finally the Ne atom
comes to ground state through collision with
tube wall and undergoes non radioactive
•transition.
He-Ne LASER ( WORKING ).

14. Application:
•The Narrow red beam of He-Ne laser is
used in supermarkets to read bar codes.
•The He- Ne Laser is used in Holography in
producing the 3d images of objects.
•He-Ne lasers have many industrial and
scientific uses, and are often used in
laboratory demonstrations of optics.
He-Ne Laser (Application).

15. 3. SEMI CONDUCTOR LASER
INTREODUCTION:
 Stimulated, organized photon emission occurs when two electrons
with the same energy and phase meet. The two photons leave with
the same frequency and direction.
 In 1916 Einstein devised an improved fundamental statistical theory
of heat, embracing the quantum of energy. His theory predicted that
as light passed through a substance it could stimulate the emission
of more light. This effect is at the heart of the modern laser.
 Mainly there are two types in semiconductor laser:
(1)Homo junction laser
(2)Hetero junction laser

16. PUMPING:
When PN junction diode is forward biased, the electrons
from ‘n’ region and holes from ‘p’ region recombine with
each other at the junction .
During the recombination process light radiations (photons)
is released from certain specified direct band gap
semiconductors like Ga-As.
This radiation is called recombination radiation and the
corresponding energy is called activation energy.
Ga-As LASER

17. METALLIC LAYER
GaAs CONTACT LAYER
Ga AlAs BARRIER LAYER
Ga As CONTACT LAYER LASERBEAM
GaAlAs BARRIER LAYER
GaAs CONTACT LAYER
+ -
GALLIUM ARSENIDE LASER
Ga- As Laser Construction

18. WORKING:
When the forward bias is applied to the metallic layer through contact
points. The electric field is produced. This electric field causes the
electrons to move from lower band of energy towards high band of
energy level.
Population inversion take place at the higher band of energy level and
when the electrons falls back at the lower energy band, it emits light,
through the polished end of the laser.
Cross reflection of the light take place which multiplies strength of
laser beam. At the end strong beam of laser comes out through the
partially polished end.
Ga-As LASER

19.  Advantages of semiconductor laser
 It is very small in dimension.
 The arrangement is simple and compact.
 It exhibits high efficiency.
 Disadvantages of semiconductor laser
The output is usually in the form of wide beam.
The purity & mono chromaticity are poorer than
other type of laser.

20. Applications:
Semiconductor diode lasers used in CD
and DVD players.
Fiber optic transceivers are manufactured using
alternating layers of various III-V and II-
VI compound semiconductors to form lasing hetero
structures.
Used in laser printers & in laser diodes.

21. THANK YOU.....