Why helium neon laser is better than ruby laser

Helium neon laser is better than ruby laser or most of the four level lasers are better than three level lasers due to the following reasons:

  • The laser output is continuous in the case of helium-neon laser. But it is in the form of pulse in the ruby laser.
  • Ruby laser requires high power pumping source, whereas Helium-neon laser requires low power pumping source like electric discharge.
  • Efficiency of helium-neon laser is more than ruby laser.
  • The defects due to crystalline imperfections are also present in the ruby laser. But it is not so in the helium-neon laser.

Reference: This article is referred from my authored book “optics and lasers” having ISBN 81-272-2948-2. In case of any doubt, post in the comment section.

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Three level lasers

In the three level laser system, the atoms are pumped from the ground state E1 to higher state E3 with the help of pumping source. The E3 is called pumping state. The life time of atoms is least in the energy level E3. It means E3 is unstable stable state and here atoms stay for 10-9 (ten power -9) to 10-8 seconds.

Atoms make transition from level E3 to E2. Energy level E2 is the metastable state (having life time 10-5 to 10-3 seconds). Thus, population of atoms become more in the energy state E2 as compared to E1.

The stimulated emission occurs between E2 and E1 producing laser. E2 is known as upper laser level (ULL) and E1 is known as lower laser level (E1).

The example of three level laser is ruby laser.

Drawback of three level laser system: Continue reading “Three level lasers”

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