LASER-2_Population-Inversion_Laser-Principle.pdf

❑ Population inversion
❑ Metastable state
❑ Laser Principle
❑ Main components of Laser

Galgotias College of Engineering & Technology

___________________________________
Dept. of Physics
Galgotias College of Engineering and Technology, Gr Noida

1

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Dept. of Physics
Galgotias College of Engineering and Technology, Gr Noida

2

Population Inversion

❑Normally, when the material is not excited externally, the population of the lower level or ground state(N1) is greater

than that of the upper level(N2).

❑When the population of the upper level exceeds that of the lower level, which is a reversal of the normal occupancy, the

process is called Population inversion

___________________________________
Dept. of Physics
Galgotias College of Engineering and Technology, Gr Noida

Engg. Physics

KAS101T/201T

Unit-V-LASER

CO5

❑ The system in which population inversion is

achieved is called active medium.

___________________________________
Dept. of Physics
Galgotias College of Engineering and Technology, Gr Noida

3

Population Inversion

___________________________________
Dept. of Physics
Galgotias College of Engineering and Technology, Gr Noida

Engg. Physics

KAS101T/201T

Unit-V-LASER

CO5

2

1

2

1

exp{ ( 2

1) /

}

exp(

/)

N
E

E

KT
N

N
hKT
N


=

−

−

=

−

___________________________________
Dept. of Physics
Galgotias College of Engineering and Technology, Gr Noida

4

Metastable State

___________________________________
Dept. of Physics
Galgotias College of Engineering and Technology, Gr Noida

Engg. Physics

KAS101T/201T

Unit-V-LASER

CO5

___________________________________
Dept. of Physics
Galgotias College of Engineering and Technology, Gr Noida

5

Laser Principle

➢ Pumping; Process Through which

population inversion is achieved.

➢ Population Inversion

➢ Stimulated Emission

___________________________________
Dept. of Physics
Galgotias College of Engineering and Technology, Gr Noida

Engg. Physics

KAS101T/201T

Unit-V-LASER

CO5

___________________________________
Dept. of Physics
Galgotias College of Engineering and Technology, Gr Noida

6

Main Components of Laser

___________________________________
Dept. of Physics
Galgotias College of Engineering and Technology, Gr Noida

Engg. Physics

KAS101T/201T

Unit-V-LASER

CO5

❑A pump source/Energy Source

❑Active medium.

❑Optical resonator/ cavity

___________________________________
Dept. of Physics
Galgotias College of Engineering and Technology, Gr Noida

7

Main Components of Laser

___________________________________
Dept. of Physics
Galgotias College of Engineering and Technology, Gr Noida

Engg. Physics

KAS101T/201T

Unit-V-LASER

CO5

❑A pump source/Energy Source

❑Active medium.

❑Optical resonator/ cavity

Thank you

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