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

MEISNER EFFECT ON SUPERCONDUCTORS

Meissner effect.

UNIT CELL AND LATTICE PARAMETERS

Unit cell In Crystals the arrangement of particles is described with three dimensional geometrical parallelepiped structure. The unit cell is defined as the smallest size of parallelepiped structure with minimum number of atoms. In a unit cell there are 6 faces and 8 corners. So 8 atoms are required to form a unit cell and all the 8 atoms are located at the 8 corners each. Lattice Lattice is defined as a three dimensional array of atoms. It describes the size and shape of the unit cell. Parameters of a unit cell A unit cell is described by six parameters. These parameters are three dimensions and the angles between them . The Dimensions of unit cell along three axes of a unit cell are represented by (a, b ,c) . The angle between b and c is represented by α, between a and c by β and between a and b by γ. we can identify the structure of crystal by knowing the parameters of unit cell. Properties of unit cell : 1. Unit cell is...

BRAGG'S LAW - DIFFRACTION OF X-RAYS THOUGH CRYSTAL ALTTICE

Diffraction of X-rays through crystal lattice: (Bragg’s law) X-rays are used to identify the structure of a crystal. The property of diffraction of x-rays are used in this procedure. The wave length of ordinary light is very large comparing with the value of inter planar spacing. Hence ordinary light cannot penetrate trough the lattice planes. But X-rays penetrate through the lattice planes and they are scattered by the atoms of the crystal lattice. Each atom acts as an opaque and the distance between two atoms acts as narrow slit. Hence the crystal lattice is considered as diffraction grating. When x-rays are scattered by the successive parallel planes they diffract with each other and produce diffraction pattern.by studying the diffraction pattern we can find different sets of planes located in the lattice at different directions. Bragg used X-rays to study the structure of crystals. He derived the co...

PHYSICS

Search This Blog