消逝波激励及增益耦合光纤三色激光辐射

Tricolor lasing emission from an evanescent wave pumped and gain coupled fibre laser

将石英光纤浸入低折射率的染料溶液中,泵浦光沿光纤轴向耦合进入光纤并以全反射方式沿光纤轴向传播,泵浦光的消逝波激励染料分子产生增益.由于增益区域与回音壁模式的消逝场区域在空间很好的重叠,因此显著地提高了泵浦效率,增加了沿光纤轴向的增益长度.将一根直径为265μm的石英光纤浸入三段激光染料溶液中,在622～632,504～518和427～434nm的3个波长范围内同时获得回音壁模式的激光辐射.在消逝波激励及增益耦合方式下,实现了同一根光纤中红绿蓝三色的回音壁模式激光辐射,由此形成一种新型的三色回音壁模式光纤激光器.本文同时从实验和理论方面讨论了回音壁模式激光沿光纤轴向的产生长度随泵浦能量变化的关系.

A Whispering-Gallery-Mode tricolor fiber laser is demonstrated by pumping and gain coupling with evanescent waves.The pump light is longitudinally coupled into a bare optical fiber immersed in a dye solution of lower refractive index.The dye molecules around the bare fiber are excited by the evanescent waves of pump light when their propagating along the fiber in a total internal reflection.Because the excited molecules are located within the evanescent field of Whispering-Gallery-Mode,a good spatial overlap between the dye gain and the evanescent field leads to a high pumping efficiency and a longer gain distance along the fiber.Once the bare fiber is inserted into three glass tube filled with Rhodamine 640,Coumarin 500 and Stilbene 420 dye solutions,respectively,Whispering-Gallery-Mode lasing oscillations at the wavelengths of 622-632 nm,504-518 nm and 427-434 nm occur simultaneously,and a tricolor lasing emission is achieved in a single optical fiber.The relationship between produced length of lasing emission and pumping energy has also been investigated.