Stimulated Emission from the Excitonic Molecules in CuCl

We report observation of efficient stimulated emission (gain {~} 10⁴ cm^-1) from recombination of excitonic molecules. This emission is obtained near 3.16 eV (3920 {}) in optically excited CuCl crystals and shown to be stimulated by use of a recently described technique employing a variable excitation length. These results in CuCl point out the importance of excitonic molecules in intrinsic stimulated-emission processes in semiconductors.