鉴于单向环形腔是目前获得较大功率单纵模激光最有效的方式之一, 为使环形腔单向运行, 需要在环形腔内插入对正反2个方向的光产生损耗差的光学元件。采用激光二极管泵浦Nd∶YAG晶体, 用声光调制器作为光学二极管使环形腔单向运行, 实现四镜矩形环形腔单纵模激光器。实验中谐振腔的稳定性由增益介质的热透镜保证, 声光调制器给正反2个方向的光提供损耗差, 这使得在竞争过程中有较大损耗的光不能运行从而获得单向输出。实验获得了连续功率1 W、光束质量因子M2为1.21 的1.06 μm单纵模激光。

Using unidirectional ring resonator is the most promising way to get high power single-longitudinal-mode (SLM) laser output. To enforce the single-longitudinal-mode ring cavity to operate unidirectionally, a component which can introduce loss difference between the counter-propagating beams in the cavity is necessary. A diode-pumped Nd∶YAG SLM four-mirror rectangle ring laser was experimentally demonstrated. The stability of the cavity was ensured by the thermal of the gain medium, and an intra-cavity acousto-optic modulator was used as the optical diode, which provided different losses on the counter-propagating beams. The beam with larger loss died out in their competition for the gain and hence the unidirectional operation was demonstrated. An SLM output power of 1 W at 1.06 μm with a beam quality factor M2 of 1.21 was obtained. The considerable increased output power and compact architecture are especially important for future practical application.