The genesis of lasing, as an evolution of the laser hybrid eigenstates comprised of electromagnetic modes and atomic polarization, is considered. It is shown that the start of coherent generation at the laser threshold is preceded by the formation of a special hybrid state at the lasing prethreshold. This special state is characterized by an enhanced coupling among excited atoms and electromagnetic modes. This leads to an increase in the rate of stimulated emission in the special state and, ultimately, to lasing. At the lasing prethreshold, the transformation of hybrid eigenstates has the features of an exceptional point (EP) observed in non‐Hermitian systems. The special state is formed when eigenfrequencies of two hybrid states coalesce or come close to each other. Below the prethreshold, lifetimes of all hybrid states grow with increasing pump rate. When the pump rate crosses the prethreshold, resonance trapping occurs with the lifetime of the special state continuing to increase while the lifetimes of all other eigenstates begin to decrease. Consequently, the latter eigenstates do not participate in the lasing. Thus, above the prethreshold, a laser transitions into the single‐mode regime.

中文翻译：

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异常阈值的特殊点

考虑到激光的发生，这是由电磁模和原子极化组成的激光混合本征态的演化。结果表明，在激光阈值处开始相干生成之前，在激光阈值之前形成了特殊的混合态。这种特殊状态的特征是激发原子与电磁模之间的耦合增强。这导致在特殊状态下受激发射的速率增加，并最终导致激光发射。在激增的阈值下，混合本征态的转换具有在非赫密特系统中观察到的例外点（EP）的特征。当两个混合状态的本征频率合并或彼此接近时，就会形成特殊状态。在阈值以下，混合态的寿命随着泵速的增加而增长。当泵浦速度超过阈值时，会发生共振陷波，同时特殊状态的寿命会继续增加，而所有其他本征态的寿命都会开始减少。因此，后面的本征态不参与激光发射。因此，在阈值之上，激光过渡到单模态。