A light emitting device and method for making the same are disclosed. An interactive optimizer 310 searches for an optimal solution of a responsivity calculator 342 using a GA while repeatedly evaluating, interactively, responsivity outputted from the responsivity calculator 342 which receives control coefficients that affect control characteristics of the interactive optimizer 310 and outputs the responsivity. As a result, the nanocrystals are single-crystals of uniform size and single-crystal orientation. After the tightening and or tuning operation is complete, the arms or wings are securable back within the body of the drum key.