In which order do the following occur during normal laser functioning? I. The atoms' electrons jump from a low-energy orbital state to a high-energy orbital state II. Upon collision with atoms of the medium in the optical cavity, the photons are absorbed by its electrons III. Electrons in the high-energy state spontaneously return to their low-energy state, emitting the energy difference between the two states IV. Spontaneous emission occurs and results in a photon with both a random direction and phase
a) II - III - I - IV
b) III - II - I - IV
c) I- II - IV - III
d) II - I - III - IV