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LASING ACTION
N a m e : P. S i r i s h G o u d
Roll no : 24AG1A05H2
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LASER
• The acronym of laser is light amplification by stimulated emission of
radiation.
• The principal of laser is based on the phenomenon of stimulated
emission predicted by albert einstein.
• In laser the process of stimulation is used for amplification of light
waves.
• In the year 1917 Einstein theoretically proved that the process of
stimulated emission must exist.
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CHARACTERISTICS OF LASER:
• The most important and outstanding characteristics of laser as
follows, which differ the laser light from the conventional light.
• Monochromaticity:
• Laser beam is highly monochromatic. Consisting of single
wavelength and emitted in narrow beam due to stimulated emission.
• The line width of laser beams is extremely narrow. The wavelength
of light from conventional sources is usually 1 in 106.whereas for
lasers it is 1 in 1015. if the frequency of radiation is 1015.then the
width of line will be 1hz.
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CHARACTERISTICS OF LASER :
• Coherence : The light that emerges from a conventional source is in
incoherent light since they emit random wave length with no
common phase relationship. Where as waves emitted by laser
source is in phase and are of same frequency.
• Laser beam is both spatially and temporally Coherent. Spatial
coherent is measured by coherence wave length which is around
600km from a laser and for any conventional light source it is only
few cm.
• Temporal coherence is measured by coherence time which is
around 10-3sec. conventional source is 10-10sec.
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CHARACTERISTICS title
LASER
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• Intensity: The intensity of light from source can be illustrated by the
number of photons coming out from it per unit area per second.
• for a laser this is around 1022 to 1034 photons /m/sec2 whereas from
a black body at 1000K with wavelength = 6000Ao is around 1016
only.
• Directionality : It has high directional. It can travel very long
distances without divergence.
• The degree of divergence for laser is around 10-5m per 1 meter
travel Whereas intensive conventional source is 0.5m per meter
lesser divergence, higher the directionality.
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CHARACTERISTICS title style:
LASER
• Life time : The time spent by an atom in the excited energy level is
called the lifetime of that atom in that particular energy state. This is
usually would be around 10-8seconds.
• Metastable state : An excited energy state which can accommodate
atoms for a longer duration of time of the order 10-3 seconds is
known as metastable state.
• Population inverse : The condition to make the excited energy state
more populated as compared to the ground state is called popular
inversion.
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• The number of atoms(N1) present in the ground state (E1) are
usually larger than the number of atoms(N2) present in the excited
state (E2). The process of making N2>N1 is called popular inversion
• For this to happen energy has to be supplied from a external source.
• For popular inversion the following condition to prevail.
• 1. The system should possess at least a pair of energy
levels(E1&E2) such that E2 – E1 = hv
• 2. There should be continuous supply of energy to pump the atoms
to the excited states.
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COMPONENTS OF LASER
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• Pumping source : It supplies suitable forms of energy to the active
medium to achieve population inversion . There are five types of
pumping mechanisms.
• 1. Electric discharge 2 . Optical pumping 3. Atom – atom collision
• 4. Direct conversion 5 . Chemical reaction
• In a laser if the active medium is a transparent Dielectric then optical
pumping is used.
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• Active medium : it is the material in which a metastable state Is
present. With Metastable state only population inversion takes
place. Population inversion forces stimulated emission; thus a laser
beam is emitted.
• Resonator cavity : It is an enclosure of active medium which
essentially consists of two ends.
• One of the mirrors is completely reflective and other is partially
reflective.
• The resonator cavity provides optical feedback, due to the
arrangement of mirrors which make the laser beam take number of
reflections until it gets sufficient energy to come out.
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PRINCIPLE OFMaster
LASINGtitle
ACTION
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• Let us consider many number of atoms in the
excited state. The photons emitted during
stimulated emission has the same energy ,
phase, frequency and direction as that incident
photon. It results in two coherent photons of
similar properties. These two photons are now
induced stimulated emission of two atoms in
excited state(E2). There by resulting in four
photons . These 4 photons are induced four more
atoms and give rise to 8 photons etc.
• Due to stimulated emission the photons multiply
in each step giving rise to an intense laser beam
of photons that are coherent and moving in the
same direction. Hence the Light is Amplified by
stimulated emission of Radiation is termed as
LASER.
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Thank You
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