The optical relaxation is a process in which nonequilibrium electrons, excited by laser pulses and originating from near Fermi level in Cu ultrafine particles, return to the equilibrium state.

• 该现象是由薄膜中金属超微粒子内费米能级附近电子被飞秒激光脉冲激发所产生的非平衡态电子经历瞬态弛豫造成的。