TOPIC :- LASER
NAME :- SIDDHI SHRIVAS
DIVISON :- COMPUTER – C
ENROLLMENT NUMBER :- 130770107163
FACULTY NAME :-Mr. VIPUL PATEL
The Word LASER Is An Acronym For :
LASER in an acronym for Light Amplification By
Stimulated Emission of Radiation.
The first laser, namely, Ruby Laser was
demonstrated by T.H.Maiman , in the year 1960.
The discovery of laser made an enormous impact
in the scientific world and showed that the
function of optics was very much alive.
A Laser is a mechanism for emitting electromagnetic
A Laser usually emits light or visible light through a
process called stimulated emission.
A laser is a device that can produce a very narrow
intense beam of monochromatic coherent light.
The emitted beam is nearly perfect plane wave.
In short, A laser is a device that emits light through a
process of optical amplification based on
the stimulated emission of electromagnetic
CHARACTERISTICS OF LASER LIGHT
o High intensity
The light emitted from a laser is monochromatic , that
is, it is of one color/wavelength. In contrast, ordinary
white light is a combination of many colors (or
wavelengths) of light.
Lasers emit light that is highly directional , that is, laser
light is emitted as a relatively narrow beam in a specific
direction. Ordinary light, such as from a light bulb, is
emitted in many directions away from the source.
The light from a laser is said to be coherent, which
means that the wavelengths of the laser light are in
phase in space and time. Ordinary light can be a
mixture of many wavelengths.
These three properties of laser light are what can
make it more hazardous than ordinary light. Laser
light can deposit a lot of energy within a small area.
EINSTEIN EXPLAINED THE ACTION OF LASER BEAM
BASED ON QUANTUM THEORY OF LIGHT .
Production of laser light is a particular
consequence of interaction of radiation
THREE process that occur when light
Interacts with MATTER are:
o Induced Absorption.
o Spontaneous Emission.
o Stimulated emission.
1. INDUCED ABSORPTION
If a photon of energy hv is incident on the atom in
the lower state, the incident photon and gets
excited to the higher energy state E2. this process
is called induced absorption.
Normally, the higher energy state is an unstable
state so the atoms will make a transition back to
the lower energy state with the emission of a
Before absorption After absorption
THE RATE OF ABSORPTION R12 IS PROPORTIONAL
TO THE POPULATION OF THE LOWER ENERGY
LEVEL N1 AND TO THE DENSITY OF INCIDENT
RADIATION ρ. HENCE,
R12 ∝ N1ρ
WHERE B12 I STHE PROPOTINALITY CONSTANT
KNOWN AS THE PROBABILITY OF ABSORPTION OF
RADIATION PER UNIT TIME.
2. SPONTANEOUS EMISSION
In spontaneous emission the atoms or molecules
in the higher energy state E2 eventually return to
the ground state by emitting their excess energy
The process is independent of external radiation .
The rate of spontaneous emission is directly
proportional to the population of the energy level
Atom in ground stateAtom in excited state
3. STIMULATED EMISSION
When electron transits from higher level to lower
level in presence of external energy is known as
In stimulated emission a photon having energy E
equal to the difference in energy between the two
levels E2 and E1 , stimulate an atom in the higher
state to make a transition to the lower state with
the creation of second photon.
According to Einstein's, under certain condition it
is possible to force an excited atom emit a photon
by another photon and the incident light wave
must be in same phase .hence we get an enhance
beam of coherent light
STIMULATED EMISSION SPONTANEOUS EMISSION
Emission of a light photon takes
place through an inducement i.e. by
an external photon.
Emission of a light photon takes place
immediately without any inducement.
It is not a random process. It is a random process.
The photons get multiplied through
The photons do not get multiplied
through chain reaction.
It is a controllable process It is an uncontrollable process
More intense less intense
Monochromatic radiation Polychromatic radiation
BASIC CONCEPTS IN LASER :
Population inversion : is a state of achieving more
number of atoms in the excited state compared to
Pumping Spontaneous emission
Pumping : is the mechanism of exciting atoms from the
lower energy state to a higher energy state by supplying
energy from an external source
Active medium: A medium in which population inversion
is achieved for laser action is called active medium. The
medium can be solid, liquid, gas and plasma.
Optical resonators :A pair of concave mirrors placed on
either side of the discharge tube, one completely polished
and the other partially polished.
Therefore in a laser….
Three key elements in a laser
•Pumping process prepares amplifying medium in suitable state
•Optical power increases on each pass through amplifying medium
•If gain exceeds loss, device will oscillate, generating a coherentoutput
Nd (Neodymium) – YAG (Yttrium Aluminium Garnet) LASER
Doped Insulator laser refers
to yttrium aluminium
garnet doped with
neodymium. The Nd ion
has many energy levels
and due to optical
pumping these ions are
raised to excited levels.
During the transition
from the metastable state
to E1, the laser beam of
wavelength 1.064μm is
M2 – partial
Essential parts of laser:-
Yttrium Aluminium Garnet in which 1.5% of neodymium ions are
doped as impurities. Nd3+ is the lasing ion.
Two end mirrors M1 (total reflector) & M2 (output coupler)
Excitation is achieved by krypton or xenon arc lamps
Nd : YAG laser rod has a length of about 5-10 cm with a diameter 6-
9mm. It is kept at one foci of an elliptical glass tube.
Krypton arc lamp , the optical source is placed at the other foci of
the glass tube. It is provided with necessary power supply
Mirrors M1 (total reflector) & M2(output coupler) act as a resonant
cavity to produce stimulated and amplification process.
ENERGY LEVEL DIAGRAM
Simplified energy level diagram for the Nd-ion in
YAG showing the principal laser transitions
Non radiative decay
Non radiative decay
E1, E2, E3 – Energy levels of Nd
E4 – Meta Stable State
E0 – ground State Energy Level
APPLICATION OF LASER:
Drilling And Cutting
In Medical World
Lasers are device which amplify light and produce
beams of light which are very intense, directional and
Pure in colour.
Laser action is preceded by three processes namely
absorption, spontaneous emission and stimulated
They can solid state ,gas, semiconductor or liquid.
Laser can be used for many applications ,helped
people develop in many things in our daily life.