双光子过程诱导的原子相干———从反转激光到无反转激光的转换

ATOMIC COHERENCE INDUCED BY TWO PHOTON PROCESS TRANSITION FROM LASING WITH INVERSION TO LASING WITHOUT INVERSION

利用双光子过程诱导原子相干，可以简化封闭Ξ型三能级激光系统的抽运机制，只要抽运场存在．系统总可以产生激光，或产生反转激光，或产生无反转激光．在一定条件下，系统实现从反转激光到无反转激光的转换。

Abstract In this paper, the pumping mechanism in the closed Ξ type three level system can be simplified using the coherence induced by the two photon process. The system exhibits either lasing with inversion or lasing without inversion so long as there exists the pumping field. The system exhibits the transition from lasing with inverson to lasing without inversion under certain conditions. Near the transition lasing without inversion may be as efficient as lasing with inversion.