基于回音壁模式微腔的窄带激光选模技术研究

发布时间：2018-03-11 13:54

本文选题：窄带选模　切入点：回音壁模式　出处：《南京邮电大学》2016年硕士论文　论文类型：学位论文

【摘要】：随着光通信、光学传感、军工和医疗等领域的发展,高性能光纤光源成为研究热点。窄线宽光纤激光器作为高性能光纤光源重要的研究方向,由于其具有线宽窄、波长灵活、设备小巧以及可实现高功率输出等特性,成为光纤传感、雷达和光纤通信等领域的重点研究对象,对光纤激光器的窄带选模技术提出了新的要求。回音壁模式光学微腔由于其高品质因数、小模式体积、低损耗和低成本等优点,成为一种理想的窄带滤波器。本文针对回音壁模式微球腔在窄带激光选模方面的性能展开相关研究,介绍了回音壁模式微腔的起源、发展、分类和应用。论文首先阐述了几种主要的微腔耦合方法和理论模型。接着,本文利用FDTD软件仿真分析了回音壁模式均匀介质微球腔与拉锥光纤的耦合过程。为改进回音壁模式微球腔的窄带选模能力,本文提出了两种新型的回音壁模式微球腔结构:其一,提出了一种均匀介质双微球级联结构,仿真结果表明,均匀介质双微球-拉锥光纤耦合系统较均匀介质单微球-拉锥光纤耦合系统降低了输出共振谱谐振峰的峰值透射率,提高了边模抑制比,压缩了谐振峰的线宽,从而提高了整个系统的窄带选模能力。其二,提出了一种双层介质结构回音壁模式微球,即在纯SiO2均匀介质微球表面镀高折射率介质膜层,仿真结果表明,当均匀介质微球表面镀层厚度为100 nm、折射率为2.4时,镀膜微球-拉锥光纤耦合系统较均匀介质微球-拉锥光纤耦合系统降低了输出共振谱谐振峰的峰值透射率,提高了边模抑制比,压缩了谐振峰的线宽,从而提高了系统的窄带选模性能;同时,该系统还提高了光场分布中的最大能量密度,降低了微腔的模式体积。此外,本文还对仿真所使用的镀膜微球的膜层厚度进行了优化,结果表明,当膜层厚度约为180 nm时,系统性能最佳,边模抑制比达到最大值,线宽得到进一步压缩,最大能量密度大幅提升,微球腔的模式体积更小。因此,本文提出的两种改进方法均对均匀介质微球的窄带选模性能有所提升,为实际应用提供了科学依据和理论指导。最后,本文设计并搭建了回音壁模式微球腔-拉锥光纤耦合实验系统,并通过实验得到了窄带回音壁模共振谱,自由光谱范围约为1.32 nm,线宽约为0.8 pm,Q值高达2.0×106。实验表明,回音壁模式微球腔应用于窄带选模和光学滤波领域具有可行性和高效性。
[Abstract]:With the development of optical communication, optical sensing, military industry and medical treatment, high performance optical fiber light source has become a research hotspot. Narrow linewidth fiber laser is an important research direction of high performance optical fiber light source, because of its narrow line width and flexible wavelength. Because of its small size and the ability to achieve high power output, it has become an important research object in the fields of optical fiber sensing, radar and optical fiber communication. A new requirement for narrowband mode selection of fiber lasers is put forward. Due to its advantages of high quality factor, small mode volume, low loss and low cost, echo wall mode optical microcavity has many advantages, such as high quality factor, small mode volume, low loss and low cost. It is an ideal narrowband filter. In this paper, the origin and development of echo-mode microsphere cavity in narrowband laser mode selection are introduced. Classification and application. Firstly, several main methods and theoretical models of microcavity coupling are introduced. In this paper, the coupling process of homogenous dielectric microsphere cavity with tapered fiber is simulated by FDTD software. In order to improve the narrowband mode selection ability of echo wall mode microsphere cavity, In this paper, two new types of echo-wall microsphere cavity structures are proposed. First, a uniform dielectric double-microsphere cascade structure is proposed. The simulation results show that, The double microsphere tapered fiber coupling system in uniform medium reduces the peak transmittance of the resonant peak of the output resonance spectrum, increases the edge-mode rejection ratio, and compresses the linewidth of the resonant peak, compared with the uniform dielectric single-microsphere tapered fiber coupling system. Therefore, the narrow band mode selection ability of the whole system is improved. Secondly, a double-layer dielectric structure echo wall mode microsphere is proposed, which is coated with high refractive index dielectric film on the surface of pure SiO2 homogeneous dielectric microsphere. The simulation results show that, When the coating thickness and refractive index of uniform dielectric microspheres are 100 nm and 2.4, the peak transmittance of the resonant peak of the output resonance spectrum is reduced in the coated microsphere tapered fiber coupling system compared with the uniform dielectric microsphere tapered fiber coupling system. The edge-mode rejection ratio is increased, the linewidth of the resonant peak is compressed, and the narrowband mode selection performance of the system is improved. At the same time, the maximum energy density in the optical field distribution is increased, and the mode volume of the microcavity is reduced. The film thickness of the coating microspheres used in the simulation is optimized. The results show that when the film thickness is about 180 nm, the system performance is the best, the side mode rejection ratio reaches the maximum, and the line width is further compressed. The maximum energy density is greatly increased, and the mode volume of the microsphere cavity is much smaller. Therefore, the two improved methods proposed in this paper have improved the narrowband mode selection performance of the homogeneous dielectric microspheres, and provided scientific basis and theoretical guidance for practical application. In this paper, an experimental system of microsphere cavity and tapered fiber coupling with echo wall mode is designed and built. The resonant spectrum of narrow band echo wall is obtained by experiments. The free spectrum range is about 1.32 nm, and the line width is about 0.8 pmQ as high as 2.0 脳 106. The microsphere cavity with echo wall mode is feasible and efficient in narrow band mode selection and optical filtering.
【学位授予单位】：南京邮电大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TN24

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