- #1
James Brady
- 105
- 4
I'm a novice studying laser physics and I came a across the condition for optical gain:
[tex]\frac{N_2}{g_2} > \frac{N_1}{g_1}[/tex]
This is a basic set up where N_1 is the number of atoms in the lower energy state and N_2 is the number of atoms in the higher energy state. g_1, and g_2 are the degeneracies for the two states respectively. I understand that for optical gain you need N_2 to be higher than N_1, but why are the degeneracies factored in? It seems like it the number of possible ways to be in a certain energy state shouldn't matter, only the number of states themselves.
Can someone explain why the degeneracies are in the denominators? I do not see why having many possible ways to obtain an energy state would effect that states relative population. Also, I guess the key term which we are trying to achieve for a laser is "population inversion" or having more atoms in the high state than the low state.
[tex]\frac{N_2}{g_2} > \frac{N_1}{g_1}[/tex]
This is a basic set up where N_1 is the number of atoms in the lower energy state and N_2 is the number of atoms in the higher energy state. g_1, and g_2 are the degeneracies for the two states respectively. I understand that for optical gain you need N_2 to be higher than N_1, but why are the degeneracies factored in? It seems like it the number of possible ways to be in a certain energy state shouldn't matter, only the number of states themselves.
Can someone explain why the degeneracies are in the denominators? I do not see why having many possible ways to obtain an energy state would effect that states relative population. Also, I guess the key term which we are trying to achieve for a laser is "population inversion" or having more atoms in the high state than the low state.