Why Are Only He Atoms Excited in He-Ne Lasers?

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SUMMARY

In He-Ne lasers, only helium (He) atoms are primarily excited due to their lower excitation energy compared to neon (Ne) atoms. While Ne atoms can be excited through collisions with He atoms, they do not achieve a sufficient population inversion on their own to sustain continuous stimulated emission. The energy transfer mechanism between excited He atoms and Ne atoms is crucial for the laser operation, allowing Ne to contribute to the laser line despite its higher excitation threshold.

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  • Understanding of laser physics and operation principles
  • Knowledge of atomic excitation and energy levels
  • Familiarity with population inversion concepts in lasers
  • Basic principles of gas dynamics in laser mediums
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  • Research the energy levels and excitation mechanisms of helium and neon atoms
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Physicists, laser engineers, and students studying optical engineering or laser technology will benefit from this discussion.

djef
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hallo all,
I was wondering the following thing: when using a He-Ne laser, you pump some energy in the system to get the He excited, but why only the He atoms?

If you pump energy in the systems, wouldn't the Ne atoms get excited too ? (and I am not speaking about them getting excites because the collisions with the He atoms).


Is this simply because it takes less energy to get the He atoms excited then the Ne atoms (though , the difference is very very small)
 
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Perhaps some of the Ne atoms do get excited by themselves, but not sufficiently so as to have a constant population inversion. It is the many surrounding excited He atoms that allow the population inversion to be sufficient for continuous stimulated emission to occur.
 
He-Ne lasers are interesting, and more complicated than the typical 'laser' diagram- which is odd considering how common they are.

A key step is the collision of He and Ne atoms to transfer energy- the He atoms are excited, collide with Ne atoms, and the Ne atoms produce the laser line:

http://en.wikipedia.org/wiki/Helium-neon_laser
 

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