Rami Arieli: "The Laser Adventure"

Rami Arieli: "The Laser Adventure" Chapter 3.2 page 4

Example 3.1: Helium-Neon Laser
Figure 3.4 show the energy level diagram of Helium-Neon laser, with the possible transitions.
The mass of the Helium atom is about one-fifth of the mass of the Neon atom.
The amount of Helium in the tube is about 6 times the amount of Neon. Thus Helium atoms have more chance to receive energy from the accelerated electrons, and transfer into the excited energy levels E₃ and E₅.

Figure 3.4: Energy Level Diagram of Helium-Neon Laser Neon atom have two excited energy levels (E₃ and E₅) which are very close to the excited energy levels of the Helium atom. The excited Helium atoms transfer their excitation energy to the Neon atoms by collisions - Resonance excitation.

Energy from the He-Ne laser is emitted at wavelengths which correspond to the energy difference between the levels:

E₅ - E₄ = > l₁ = 3.391 [mm] E₅ - E₂ = > l₂ = 0.632 [mm] E₃ - E₂ = > l₃ = 1.152 [mm] Later we shall understand how to choose the specific required wavelength at the output of the laser.