Laser Physics Lecture -3

Prof. Zohaib Metla

What is the matters and what a kind of a changes does a matter in the undergo?
in the Everything that in the has mass and volume is called a matter. All matter, in the regardless of state, in the undergoes physical and in the chemical changes. These changes can be in the microscopic or in the macroscopic.

Achieving inversion:  Pumping in the laser medium

More details see below diagrma pic

 
Different b/w LASER MATTER INTERACTION and
Laser INDUCED PLASMA in diagram
More details see below diagrams pic

 
Laser Ablation Response on materials diagrams 

 
Radiative  decay
When this  energy  is  delivered in the  form  of an in the electromagnetic (em)  wave,  in the process is  called  spontaneous in the  (or  in the radiative)  emission.
in the Spontaneous  emission  is  therefore in the  characterized by  the emission  in the a  photon  of energy
Nonradiative  decay
In The  energy  difference E2 – El is in the  delivered  in the some form of energy  in the other than em in the radiation  (e.g., it may in the go into  in thekinetic in the  or internal in the energy  of the  surrounding in the atoms  or molecules).
 
Probabilities  for Spontaneous, Stimulated and  Absorption, emission
Spontaneous  Decay:
in the rate  in the of decay  of the  upper state in the  population (dN2/dt)sp must be in the proportional toin the  the  population N2.
where in the minus sign  in the accounts  for  the  fact  that  in the time in the  derivative  is  negative.  The  coefficient A, in the introduced  in  this  way, is  a  in the positive constant called  the in the  rate  of spontaneous  emission  or
the  Einstein A  in the coefficient.
 

For  nonradiative  decay
in the  Spontaneous emission of the numerical V value of A  (and  b    )  depends only on the particular in the transition considered.  For nonradiative decay,  on in the other hand,      depends not  only  on in the  transition  but  also  on in the characteristics  of the surrounding in the  medium.
Stimulated emission:
where ( in the  dN2/dt)st is the rate at which transitions 5 to  1 occur as a  result  of stimulated emission and W21 is  the  rate of stimulated in the  emission.
Unlike  A, however,  W21 depends  not  only  on in the  particular in the  transition  but  also  on the  intensity in the  of the  incident  em wave in the  absorption