无需隔离器的单向运行光纤环形激光器的研究

从理论上设计并从实验上实现了一种简单易行的环形谐振腔结构，它仅由两个耦合器连接成一个环形谐振腔，可以使得逆时针运行光的增益高于顺时针运行光的增益，其比值取决于两个耦合器耦合比的选取。将此作为掺铒光纤激光器的谐振腔，由于两个相反方向具有不同的损耗，因而可以实现在不需要隔离器的情况下也能保证激光的单向运行，从而简化了器件结构，消除隔离器的插入损耗，降低了成本。在实验的过程中使用两个3dB耦合器，结果表明，在阈值及其以上抽运功率下，两个相反方向的输出功率差始终大于17dBm，基本实现了激光的单向运行。

Study on a Fiber Ring Laser with Unidirectional Operation without Isolator

An erbium doped fiber ring laser with unidirectional operation without optical isolator has been investigated theoretically and experimentally. The fiber ring laser cavity is only composed of two couplers and built in such a way that it offers a higher counterclockwise over clockwise circulating gain ratio, which is strongly dependent on coupling coefficients of the two couplers. The optical fields propagating in the two directions suffer from different losses. As a consequence, the laser oscillation appears in a quasi unidirectional form without isolators. So, the structure of the fiber ring laser is simplified, eliminating the insertion loss arising from the isolator and decreasing the cost. Two 3 dB couplers are used in the experiment, in which the result shows that on and above the threshold of pump power, there is a difference in the output power of 17 dBm between two contrary directions, basically realizing the unidirectional operation of the fiber laser.