Ce∶KNSBN光折变光纤两波耦合特性研究

Study on Properties of two-wave Coupling with Ce∶KNSBN Photorefractive Fiber

研究了掺铈钾钠铌酸锶钡 (Ce∶KNSBN)光折变光纤“扇”特性及两波耦合的基本特性。通过实验发现 ,当入射光的入射角为 8°左右时 ,“扇”最小 ,这与块状晶体有根本的不同。在信号光与抽运光的入射夹角 2θ小于 11°时 ,两波耦合增益随入射夹角的增大而增大 ,而当入射夹角大于 11°时 ,两波耦合增益随着入射夹角的增大而迅速减小。给出了在各个不同的入射夹角下 ,两波耦合增益中透射的信号光的时间特性曲线。两波耦合增益随信号 抽运比的增加而增加 ,在入射夹角为 8° ,信号 抽运比为 1∶10 0 0时 ,两波耦合增益达到了 77,比块状晶体相应条件下提高了 4倍。用两波耦合的理论公式对增益随信号 抽运比的实验数据进行了拟合 。

Properties of fanning effect and two wave coupling in a Ce∶KNSBN photorefractive fiber were studied. It is found that the fanning is weak when the incident angle is about 8°, which differs from that in a bulk crystal. Two wave coupling gain increases as the angle between pump beam and signal beam increases when the angle is less than 11°. It decreases as the angle increases when the angle is greater than 11°. The time evolution of transmitting signal beam at different angles was also given. The two wave coupling gain is 77 in the conditions that the angle is 8° and the signal to pump beam intensity ratio is 1∶1000, which is about 4 times that in a bulk crystal in the same conditions. The theoretical fitting and the experimental data are coincident quite well.