消逝波激励及增益耦合的柱形微腔回音廊模激光辐射

毛细管的折射率比溶液的折射率高,石英毛细管在被插入的溶液中形成圆柱形微腔。采用近轴向消逝波抽运的方法,使激光的染料增益局限于抽运光在染料区的消逝场范围内,极大地提高了消逝波耦合柱形微腔的抽运效率。与侧向抽运方式比较,柱形微腔回音廊模(WGM)激光的抽运阈值从200μJ降低到9.5μJ。实验所得到的激光谱线波长以及相邻谱线的波数间隔与回音廊模式的理论计算吻合,说明石英毛细管能得到与石英光纤类似的柱形微腔回音廊模激光辐射。

Whispering-Gallery-Mode Laser of Evanescent Wave Exciting and Coupling Dye Gain in Cylindrical Microcavity

A cylindrical microcavity was made by immersing a silica capillary in a solution of rhodamine 6G whose refractive index is lower than capillary′s. Whispering-gallery-mode (WGM) laser was observed in the cylindrical microcavity by evanescent wave exciting and coupling dye gain. Due to dye gain was excited by a pumping evanescent wave, the gain was limited around the cylindrical microcavity closely, and the pumping efficiency was then improved greatly. The pumping threshold for laser emission was reduced to 9.5 μJ in this method compared with a value of 200 μJ in a method of only evanescent wave coupling dye gain. Wave number intervals of whispering-gallery-modes between measured and theoretic values matched very well. The calculated positions of structural resonances of whispering-gallery-modes matched the experimental results very well too. All those indicated when silica fiber was replaced by silica capillary as cylindrical microcavity, the same whispering-gallery-mode could also be obtained.