Unit-2 Lasers and Applications
LASER Light Ampli fica tion by simula ted emission
of Rediation
dimple light ocoherent: 5ame uwovelength
non-monochromatic : Single wavelengh
High energ94
non-direchional
Laser lighb is coherent that
too highly
Also, highly mono-chromaic
highly enetgyitic
highly direcHona l (very Small divergence)
Interaction of Light oith Materials
Absorphion of light AE room temperahute
mote mo0st of energy
E
Energy levels level stays at E
phofon
LOhen a phoron of
phoon moving from low leve
enegytha) (ho) falls
Fo high leve
On this aom
I t is complelely absorb phoon & jumps from
E, to E2 This is called absorbshion of phoons
pholons
Robabiliby of occurence of absorphon of tadiahon
rom state to stale 2 is
Pa u)
ohere, U(9) > enerqy
densi ty
density
, Here, Ba Einstein co-efficient of absorption of radiahion
Spon taneous emission
ife time of elecron 10
Thereore, stays in ne enerqy level for this hime
And again it goes into louoer enetgy level
And
(E-h)
A n elechon stay 10 in exicred state (Ea)
AHter tha gain goes to looer energy state by
O
in random direchon
cmitting a phoon
.h E, E,
Therefore, it is Knoon as spontaneous emission
of radiah on-
spontaneous emission
robability of OCCutrence of
o staleI is
radiaion om state 2
aconstant )
Pi2 Aai-
1ad
Ao Eins tein co-cficfent of spontaneovs emission
Simulated Emission ( discoveve by eie stein
an elecron is in the exicted state E
Suppose,
be simulate d by a pho ton havinq
This can
to Hre 9
the
en
ergy Ch E-E)
Tuoo Phoons
Phorons oof
hen when ejumps from E to EToo
emibted in 3ame dircchon
Same
Odme Cn eigy oil) be
eneigy
LASER Light Ampli fica tion by simula ted emission
of Rediation
dimple light ocoherent: 5ame uwovelength
non-monochromatic : Single wavelengh
High energ94
non-direchional
Laser lighb is coherent that
too highly
Also, highly mono-chromaic
highly enetgyitic
highly direcHona l (very Small divergence)
Interaction of Light oith Materials
Absorphion of light AE room temperahute
mote mo0st of energy
E
Energy levels level stays at E
phofon
LOhen a phoron of
phoon moving from low leve
enegytha) (ho) falls
Fo high leve
On this aom
I t is complelely absorb phoon & jumps from
E, to E2 This is called absorbshion of phoons
pholons
Robabiliby of occurence of absorphon of tadiahon
rom state to stale 2 is
Pa u)
ohere, U(9) > enerqy
densi ty
density
, Here, Ba Einstein co-efficient of absorption of radiahion
Spon taneous emission
ife time of elecron 10
Thereore, stays in ne enerqy level for this hime
And again it goes into louoer enetgy level
And
(E-h)
A n elechon stay 10 in exicred state (Ea)
AHter tha gain goes to looer energy state by
O
in random direchon
cmitting a phoon
.h E, E,
Therefore, it is Knoon as spontaneous emission
of radiah on-
spontaneous emission
robability of OCCutrence of
o staleI is
radiaion om state 2
aconstant )
Pi2 Aai-
1ad
Ao Eins tein co-cficfent of spontaneovs emission
Simulated Emission ( discoveve by eie stein
an elecron is in the exicted state E
Suppose,
be simulate d by a pho ton havinq
This can
to Hre 9
the
en
ergy Ch E-E)
Tuoo Phoons
Phorons oof
hen when ejumps from E to EToo
emibted in 3ame dircchon
Same
Odme Cn eigy oil) be
eneigy
