LASER
MODULE 5
, Introduction
Conventional light sources : Poor coherence
For an intense beam of radiation : LASER
LASER : LIGHT AMPLIFICATION BY STIMULATED
EMISSION OF RADIATION
RUBY LASER (Solid State Laser) : THEODORE MAIMAN
GAS LASERS : He-Ne, CO2 laser
SEMI CONDUCTOR LASER : Ga As
Application In the field of Communication
Industrial Application
In the field of Medicine
, Absorption
E2 E2
hγ = E2-E1
E1 E1
N1 = No,of atoms in the ground sate
Rab α N1ρ(γ) ρ(γ)= The photon density
B12 = The Einstein’s coefficient of absorption
Rab = B12 N1ρ(γ)
Intensity of incident radiation decreases
, Spontaneous Emission
Before Emission After Emission
During emission
It is a random process.
E2
Emitted photons can’t am
each other.
E1 It is not possible for us to
Atom in excited intense beam of radiation
Atom in ground
state state
N2 = No.of atoms in the excited state
Rsp α N2
A21 = Einstein’s coefficient of spontaneous
Rsp = A21N2 emission
MODULE 5
, Introduction
Conventional light sources : Poor coherence
For an intense beam of radiation : LASER
LASER : LIGHT AMPLIFICATION BY STIMULATED
EMISSION OF RADIATION
RUBY LASER (Solid State Laser) : THEODORE MAIMAN
GAS LASERS : He-Ne, CO2 laser
SEMI CONDUCTOR LASER : Ga As
Application In the field of Communication
Industrial Application
In the field of Medicine
, Absorption
E2 E2
hγ = E2-E1
E1 E1
N1 = No,of atoms in the ground sate
Rab α N1ρ(γ) ρ(γ)= The photon density
B12 = The Einstein’s coefficient of absorption
Rab = B12 N1ρ(γ)
Intensity of incident radiation decreases
, Spontaneous Emission
Before Emission After Emission
During emission
It is a random process.
E2
Emitted photons can’t am
each other.
E1 It is not possible for us to
Atom in excited intense beam of radiation
Atom in ground
state state
N2 = No.of atoms in the excited state
Rsp α N2
A21 = Einstein’s coefficient of spontaneous
Rsp = A21N2 emission
