摘要
近年来,光子学微结构中的柱/碟、环/线、球等几何微腔已在微腔激光器件和光谱技术应用中取得重大进展。本文将熔锥光纤与球/柱微腔作为一个有机的整体进行耦合实验研究,发现了吸收光谱中等间距的分立的结构共振峰,并且进一步对共振峰的特点进行了实验研究。
我们首先回顾了近年来球/柱微腔特性的研究状况和微腔耦合器的近期发展,并对微腔的应用情况进行简要介绍。
其次,我们从理论的角度出发,利用Mie散射理论得到了球微腔内外的电磁场分布,分析了球微腔的有关特性,再把球微腔的相关理论近似应用在柱微腔的分析中,对实验的开展有非常重要的指导意义。接着对熔锥光纤的理论进行探讨,从一般光纤的场解入手,推导出弱导光纤和熔锥光纤锥腰的场解。
然后根据微球与熔锥光纤场模的分布构造了微球与熔锥光纤的耦合系统,从场传输耦合方程推导了耦合系统的透射率。讨论了球微腔与熔锥光纤的间距等因素对耦合系统的透射率的影响。并分析了耦合系统的三种耦合情形:欠耦合、临界耦合、过耦合。
再次,我们设计了CO_2激光熔融与拉制熔锥光纤的系统,制备了实验需要的熔锥光纤,将系统进行扩展,制备了石英球/柱微腔。将上海光机所提供的掺铒磷酸盐玻璃进行高温熔融抽丝,选择直径适当的玻璃丝进行断面处理,再利用扩展的系统烧制出掺铒玻璃球微腔。
最后,我们搭建了耦合实验需要的平台,先将石英球微腔与熔锥光纤进行耦合,发现了明显的回廊模式结构共振峰,并对共振峰的模式分裂现象进行了研究。然后详细的介绍了掺铒磷酸盐玻璃球微腔与熔锥光纤耦合实验,对其吸收光谱上结构共振峰的波长、峰间间距以及光反馈进行研究。同时,对柱微腔与熔锥光纤的耦合系统进行了实验研究。
本论文工作得到国家自然科学基金资助,项目名称:“稀土掺杂氟化物玻璃球微腔激光器”,项目编号:60277026。
In recent years,optical microcavities such as microcylinder,microdisk, microring,microsphere have been greatly developed in microcavity laser and spectrum technology.In this thesis,the microsphere/microcylinder and the tapered fiber coupling system,are regarded as the object of study.The discrete structural resonance in the silica microsphere/microcylinder and glass microsphere doped by Er3+ is experimentally observed.Then we studied more about the characteristics of the resonance.
This thesis consists of the following five parts of work.
Firstly,we had a brief review on the history of microsphere/microcylinder resonance in theoretical and experimental studies.Then we introduced simply the applications of the microcavity.
Secondly,according to the Mie's scattering theory,the optical field in a microsphere has been obtained.The characteristics of the microspherical resonance and the biconical tapered fiber have been analyzed separately.The theory of microsphere has been approximately applied to the study of microcylinder.Then the field solution of biconical tapered fiber has been obtained.
Next,the coupling system between microsphere and tapered fiber has been analyzed theoretically.The transmission ratio of the coupling system and its dependence on the gap between microsphere and biconical tapered fiber have been discussed.The coupling system consists of critical coupling,excess coupling and deficient coupling.
And next,the CO_2 laser system of drawing the biconical tapered fiber has been designed,and the biconical tapered fiber that we need has been made.Then we improved the system to fabricate silica microsphere/microcylinder.Using the Er~(3+)-doped phosphate bulk glass,the Er~(3+)-doped phosphate glass microsphere is fabricated by this CO_2 laser system.
At last,the coupling system has been set up.The laser light is coupled into the silica microsphere by a biconical tapered fiber.The discrete structural resonance in the absorption spectra was observed,and then the splitting effects of the modes were analyzed.Then the coupling experiment of Er~(3+)-doped phosphate glass microsphere with biconical tapered fiber has been studied in detail.The measured wavelengths,the interval between the adjacent modes and the feedback have been compared with the theoretical computation,and they are fair coincident with each other.Lastly,the coupling of microcylinder and biconical tapered fiber has been studied briefly.
The research of this dissertation is supported by National Natural Science Foundation of China.number 60277026.
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