高功率隔离器单模与多模工作退偏特性

Depolarization in high power Faraday isolators with single mode and multi-mode laser incidences

以传统结构隔离器为模型,应用琼斯理论,比较分析了单模与多模激光入射时高功率隔离器热致退偏特性。研究结果表明:高功率隔离器热致退偏可分为线性双折射致退偏与圆双折射致退偏;两种退偏均与入射激光功率的平方成正比;在光功率一定的条件下,线性双折射致退偏不随光斑半径的变化而变化,圆双折射致退偏随光斑半径的增大而减小;在其它条件相同的条件下,多模光场能够有效地降低隔离器热致退偏,多模时线性双折射致退偏仅为单模时退偏的60%,圆双折射致退偏也比单模时要小,减小幅度随光斑半径的增加而增加。

Employing Jones theory,thermal self-induced depolarization in high power conventional Faraday isolators is investigated with single mode and multimode lasers.The results show that depolarization in high power isolators is composed of depolarization induced by linear birefringence and depolarization induced by circular birefringence,and both are proportional to square of laser power;with a constant laser power,depolarization induced by linear birefringence is beam radius independent,but depolarization induced by circular birefringence increases with decrease of beam radius.Both depolarizations are reduced by multimode incidence.Depolarization induced by linear birefringence with multimode incidence is only 0.6 times that with single mode.Reduction of depolarization induced by circular birefringence is more effective with larger beam radius.