根据耦合波理论,在分析分布反馈(DFB)光纤激光器纵模特性的基础上,着重阐述其偏振特性。另外给出了偏振态同耦合系数和双偏振态相移量差的关系。理论分析结果表明,当分布反馈光纤激光器输出为0阶模时,输出激光的偏振状态由耦合系数和双偏振态的相移量差共同决定,即在耦合系数一定的情况下,通过增加双偏振态相移量的差,或在双偏振态相移量差一定的情况下,通过减小耦合系数,可以实现单偏振输出。实验中在经载氢处理的掺铒光纤上制作分布反馈光纤激光器,由于耦合系数较大和双折射效应过小,输出为双偏振态。

Based on the analysis of longitudinal modes of distributed feedback (DFB) fiber lasers, the polarization properties are investigated extensively using the conventional coupled wave theory. The relationships between polarization states, coupling coefficient and phase-shift dispersion of dual polarization states are reported. It shows that when lasers operate at the fundamental mode, the states of polarization are determined by both coupling coefficient and phase shift dispersion of dual polarization states. Single polarization output can be obtained by increasing the phase-shift dispersion under a certain coupling coefficient, or by decreasing the coupling coefficient under a certain phase-shift dispersion. DFB fiber lasers are fabricated in hydrogen-loaded erbium-doped fibers, the output laser has dual polarization states due to large coupling coefficient and extremely low birefringence.