Stimulated emission divided by the input intensity: Substituting this definition into the prior equation, we find the general gain equation: In the special case where the input signal is small compared to the saturation intensity, in other words, then the general gain equation gives the small signal gain as or which is identical to the small signal gain equation (see above). For large input signals, where the gain approaches unity and the general gain equation approaches a linear asymptote: .3 Laser Fundamentals, William T. Silfvast Stimulated emission Stimulated emission is the process by which an incoming photon of a specific frequency can
Stimulated emission difference in energies between the two states as a photon. The photon will have frequency "ν" and energy "hν", given by: where "h" is Planck's constant. Alternatively, if the excited-state atom is perturbed by an electric field of frequency "ν", it may emit an additional photon of the same frequency and in phase, thus augmenting the external field, leaving the atom in the lower energy state. This process is known as stimulated emission. In a group of such atoms, if the number of atoms in the excited state is given by "N", the rate at which stimulated emission occurs is