When nonradiative depopulation is not zero (in fact it is usually true), it is not linearly even for an ideal four-level laser system in the closed microcavity.

• 当无辐射衰减速率不为零时(实际上往往如此),即使对理想的四能级激光系统的封闭腔,它的光输出特性也不再是线性的。