07-04-2012, 10:54 AM
Helium-neon Laser
[attachment=19668]
Historical facts
The Helium-Neon laser was the first continuous laser.
It was invented by Javan et. al. in 1961. But how did Javan manage to do this?
This shows that it is no coincidence that Javan's first He-Ne laser oscillated at a
Wavelength of 1.5μm, since the amplification at this wavelength is considerably
Higher than the 632 nm line which is reached at what is now commonly known as the red line, which was made to oscillate only one year later by White and Ridgen.
The similarity between the manufacturing techniques of He-Ne lasers and electron valves helped in the mass production and distribution of He-Ne lasers..
It is now clear that He-Ne lasers will have to increasingly compete with laser diodes in the future. But He-Ne lasers are still unequalled as far as beam geometry and the purity of the modes are concerned. Laser diodes will have to be improve to a great extent before they pose a serious threat to helium-
Introduction
A helium-neon laser, usually called a He-Ne laser, is a type of small gas laser. HeNe lasers have many industrial and scientific uses, and are often used in laboratory demonstrations of optics.
He-Ne laser is a four-level laser.
Its usual operation wavelength is 632.8 nm, in the red portion of the visible spectrum.
It operates in Continuous Working (CW) mode.
Construction of He-Ne laser
The setup consists of a discharge tube of length 80 cm and bore diameter of 1.5cm.
The gain medium of the laser, as suggested by its name, is a mixture of helium and neon gases, in a 5:1 to 20:1 ratio, contained at low pressure (an average 50 Pa per cm of cavity length ) in a glass envelope.
The energy or pump source of the laser is provided by an electrical discharge of around 1000 volts through an anode and cathode at each end of the glass tube. A current of 5 to 100 mA is typical for CW operation.
He-Ne Energy level diagram
The left side of the representation shows the lower levels of the helium atoms.The energy scale is interrupted and that there is a larger difference in energy in the recombination process than is evident in the diagram.
A characteristic of helium is that its first states to be excited, 21S1 and 21S0 are metastable, i.e. optical transitions to the ground state 11S0 are not allowed, because this would violate the selection rules for optical transitions. As a result of gas discharge, these states are populated by electron collisions
Applications of He-Ne laser
The Narrow red beam of He-Ne laser is used in supermarkets to read bar codes.
The He- Ne Laser is used in Holography in producing the 3D images of objects.
He-Ne lasers have many industrial and scientific uses, and are often used in laboratory demonstrations of optics.
[attachment=19668]
Historical facts
The Helium-Neon laser was the first continuous laser.
It was invented by Javan et. al. in 1961. But how did Javan manage to do this?
This shows that it is no coincidence that Javan's first He-Ne laser oscillated at a
Wavelength of 1.5μm, since the amplification at this wavelength is considerably
Higher than the 632 nm line which is reached at what is now commonly known as the red line, which was made to oscillate only one year later by White and Ridgen.
The similarity between the manufacturing techniques of He-Ne lasers and electron valves helped in the mass production and distribution of He-Ne lasers..
It is now clear that He-Ne lasers will have to increasingly compete with laser diodes in the future. But He-Ne lasers are still unequalled as far as beam geometry and the purity of the modes are concerned. Laser diodes will have to be improve to a great extent before they pose a serious threat to helium-
Introduction
A helium-neon laser, usually called a He-Ne laser, is a type of small gas laser. HeNe lasers have many industrial and scientific uses, and are often used in laboratory demonstrations of optics.
He-Ne laser is a four-level laser.
Its usual operation wavelength is 632.8 nm, in the red portion of the visible spectrum.
It operates in Continuous Working (CW) mode.
Construction of He-Ne laser
The setup consists of a discharge tube of length 80 cm and bore diameter of 1.5cm.
The gain medium of the laser, as suggested by its name, is a mixture of helium and neon gases, in a 5:1 to 20:1 ratio, contained at low pressure (an average 50 Pa per cm of cavity length ) in a glass envelope.
The energy or pump source of the laser is provided by an electrical discharge of around 1000 volts through an anode and cathode at each end of the glass tube. A current of 5 to 100 mA is typical for CW operation.
He-Ne Energy level diagram
The left side of the representation shows the lower levels of the helium atoms.The energy scale is interrupted and that there is a larger difference in energy in the recombination process than is evident in the diagram.
A characteristic of helium is that its first states to be excited, 21S1 and 21S0 are metastable, i.e. optical transitions to the ground state 11S0 are not allowed, because this would violate the selection rules for optical transitions. As a result of gas discharge, these states are populated by electron collisions
Applications of He-Ne laser
The Narrow red beam of He-Ne laser is used in supermarkets to read bar codes.
The He- Ne Laser is used in Holography in producing the 3D images of objects.
He-Ne lasers have many industrial and scientific uses, and are often used in laboratory demonstrations of optics.