Stimulated Emission & Emitted photon direction

In summary, the conversation discusses the process of stimulated emission in lasers, where a photon with the correct wavelength can cause an electron to drop from a higher to a lower energy level, emitting a new photon with the same wavelength, phase, and direction. This process is possible due to CPT symmetry and can be compared to absorption equations, as well as the concept of negative radiation pressure for pulling photons in a given direction.
  • #1
RobbyQ
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TL;DR Summary
Stimulated Emission & Emitted photon direction
I always understood that a photon of correct wavelength would raise the energy level of an electron (which is the case)
But reading about lasers and stimulated emission I read the following where the electron drops a level upon absorption:-
"A photon with the correct wavelength to be absorbed by a transition can also cause an electron to drop from the higher to the lower level, emitting a new photon. The emitted photon exactly matches the original photon in wavelength, phase, and direction. This process is called stimulated emission."

How is this possible i.e dropping to a lower energy level and how/why is the photon wavelength, phase, and direction preserved?
 
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  • #2
Stimulated emission-absorption equations would be exchanged if performing CPT symmetry, suggesting they are CPT analogs - also through B_{12}=B_{21} symmetry for their Einstein's coefficients.

If so, and absorption is from positive radiation pressure, pushing photons into a target (from given direction) ... maybe we should think about stimulated emission through negative radiation pressure, pulling of photons (in given direction)?
https://scholar.google.pl/scholar?q=negative+radiation+pressure
https://www.physicsforums.com/threads/negative-radiation-pressure.1053657/
 
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