Question

Problem 4) Consider the following laser system. It consists of a conventional 4-level system (the laser action occurs between E2 and E1 as usual with spontaneous transition time τ, between these states, and atoms in state Ei have spontaneous decay time t, back to the ground state, Eo) 32 34 E4 4 0 To obtain population inversion, atoms are pumped from state Eo to state Es. However, while some of the atoms decay to state E2 with spontaneous transition time t32, some decay into a non-lasing state Es with spontaneous transition time τ34 . This leads to a second decay pathway from E, back into the ground state with decay time τ 4 . Note: You may not assume that any of the decay times are short enough to be considered instantaneous here. You may also not assume that the ground state is so populated as to be considered infinite population density. Assuming a pump rate W from the ground state to state E3, solve for the population inversion AN-N2-N in the steady state in terms of the time constants given, the pump rate and the total population No of atoms in all states.

need help

Answer 1

て4-5 T82 t, dut lt dt 2. i + wip Tag.

3 2