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
