two excited, two at ground level : DOUBLE STIMULATED EMISSION

CORRECT !

 Stimulated emission could occur twice, after the first stimulated transitions there was a high probability that the photon(s) could stimulate another transition since the upper level was still heavily overpopulated.

What is most likely to occur when the next photon reaches the system ?

  1. Absorption
  2. Stimulated emission
  3. Processes 1. and 2. occur with equal probability.