Applied Physics I: Chapter 10: Applied Optics - Lasers
Pumping methods
Lasers | Optics
Some of the most commonly used methods are: (a) Optical pumping. (b) Electrical Pumping (Direct electron excitation). (c) Inelastic atom‒atom collision. (d) Direct conversion. (e) Chemical process
PUMPING
METHODS
Pumping:
The process of raising
more number of atoms to excited state by artificial means is called pumping
process.
There
are several methods by which the population inversion (pumping) can be
achieved. Some of the most commonly used methods are:
(a)
Optical pumping.
(b)
Electrical Pumping (Direct electron excitation).
(c)
Inelastic atom‒atom collision.
(d)
Direct conversion.
(e)
Chemical process
(a) Optical pumping:
Here, the atoms are excited with the help of photons emitted by an external
optical source. The atoms absorb energy from the photons and raise to excited
state. (e.g) Ruby Laser, Nd‒YAG Laser.
(b) Electrical Pumping:
The electrons are accelerated to very high velocities by strong electric field
and they collide with gas atoms and these atoms are raised to excited state (e.g.)
Gaseous ion lasers (argon laser), Helium‒Neon (He‒Ne) laser, CO2
Laser etc.
(c) Inelastic atom‒atom
collision: In this method a combination of two
types of gases are used, say A and B, both having the same (or) nearly
coinciding excited states A* and B*.
During
electric discharge 'A' atoms get excited due to collision with electrons. The
excited A* atoms now collide with 'B' atoms so that B goes to excited state B*
(e.g) Helium‒Neon laser, CO2 laser
e‒
+ A → A*
A*
+ B → B*+A
(d) Direct conversion:
Due to electrical energy applied in direct band gap semiconductor like GaAs
etc., the combination of electrons and holes takes place and electrical energy
is converted into light energy directly. (e.g) Semiconductor laser.
(e) Chemical method:
Due to some chemical reactions, the atoms may be raised to excited state. (e.g)
Dye laser.
Applied Physics I: Chapter 10: Applied Optics - Lasers : Tag: Applied Physics : Lasers | Optics - Pumping methods
Applied Physics I: Chapter 10: Applied Optics - Lasers
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