HELIUM AND NEON LASER

Helium and Neon laser

Construction :

Helium-Neon laser is a gas laser. A mixture of helium and neon gas in 10 : 1 ratio at the pressure of 1 mm Hg is filled in a discharge tube.
The diameter of tube is 1.5cm and the length 80 cm .
The two end of the discharge tube are provided by Brewster glass windows .
Two mirrors are arranged on either side of the discharge tube. One f the mirrors is perfect reflector where as the second mirror is a partial reflector.
The two electrodes of the discharge tube are connected to a high tension voltage , frequency generator.

Working :
When high tension voltage is applied the Helium atoms are excited to higher energy level.
These higher energy levels are meta stable states at 20.06 ev
The excited Helium atoms collide with neon atoms which are in the ground state.
The excited neon atoms will reach to three meta stable excited states. The excited ne atoms have more energy than He atoms
There is a stimulated emission which release three types of wavelengths between E5’E4’ and E3’.
During this transition 3390 A ,1550 A and 6328 A ( red ) are released.
The two wavelengths 3390 and 1550 A are absorbed by Brewster windows. The wave length 6328 A ( red ) is released as out put laser.

Advantages of He – Ne laser:
1. He- Ne laser is a continuous laser beam
2. it costs very low for manufacturing
3.it emits three wavelengths but only red 6328A is used as it is more visible.
4.it is safe as its output power is low.

Comments

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