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JD23

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- TL;DR Summary
- Both equations act on target inside laser - which ones act on external targets?

Could population inversion be achieved by shooting with (ring) laser?

Stimulated emission-absorption have two symmetric equations for population (N_1 - number of ground state atoms, N_2 - of excited) written below, at heart of lasers: https://en.wikipedia.org/wiki/Stimulated_emission#Mathematical_model

We assume that both equations act on the central target inside laser - but what about external laser's targets? (with frequencies in agreement)

Standard laser's target absorbs produced photons, increasing the number of its excited atoms (N_2) - like in the equation on the right.

But what about the second equation (on the left)? - if it also acts, the maximal achievable excitation level by shooting with laser should be N_1 = N_2, is it?

Then there are ring lasers - using optical isolator to enforce unidirectional photon trajectories - thanks to e.g. Faraday effect: difference in propagation speed for two circular polarizations (they would switch after T transform - this material violates T symmetry).

For them it seems equation on the right acts only on target on the right?

If so, they would allow for very high excitation levels for external target: N_2 > N_1 for target (population inversion, if overcoming spontaneous emission)?

And what about target on the left? Looking from perspective after T or CPT symmetry, it would become the standard target - for equation on the right, so in standard perspective shouldn't equation on the left act on target on the left?

Could population inversion be achieved by shooting with (ring) laser?

We assume that both equations act on the central target inside laser - but what about external laser's targets? (with frequencies in agreement)

Standard laser's target absorbs produced photons, increasing the number of its excited atoms (N_2) - like in the equation on the right.

But what about the second equation (on the left)? - if it also acts, the maximal achievable excitation level by shooting with laser should be N_1 = N_2, is it?

Then there are ring lasers - using optical isolator to enforce unidirectional photon trajectories - thanks to e.g. Faraday effect: difference in propagation speed for two circular polarizations (they would switch after T transform - this material violates T symmetry).

For them it seems equation on the right acts only on target on the right?

If so, they would allow for very high excitation levels for external target: N_2 > N_1 for target (population inversion, if overcoming spontaneous emission)?

And what about target on the left? Looking from perspective after T or CPT symmetry, it would become the standard target - for equation on the right, so in standard perspective shouldn't equation on the left act on target on the left?

Could population inversion be achieved by shooting with (ring) laser?

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