I have been doing more reading about the history of stimulated emission. Einstein formally introduced a quantum version of the concept in 1917. Therefore you might think that it is only possible in a quantum theoretical context. However, subsequent mathematical work has shown that a form of stimulated emission can also arise in a classical (pre-quantum) setting when a suitable model of the atom is used.
Also, it seems to me the concept of stimulated emission represents a revival of Count Rumford's cooling or frigorific radiation but under a different name. The classical physicists who developed radiation theory from the second half the 19th century onwards were ideologically opposed to Rumford's concept of cooling radiation, because at the time there were no unambiguous empirical reasons to accept or reject the concept. However, I am starting to wonder if this ideological opposition to cooling radiation contributed to the "ultraviolet catastrophe" which happened when classical physicists failed to adequately explain the blackbody radiation curve. If that is the case then perhaps Planck's ad hoc introduction of "quanta" could have been avoided if the possibility of stimulated emission or cooling radiation were incorporated into classical accounts of blackbody radiation from the outset. Harry
