A fully fiber integrated way to enhance the mode-matching is to apply optics in the form of graded-index fiber lenses, as it is presented by G.K. Gulati et al. To determine the cavity length, a multimode fiber piece of a specific size is used to terminate the assembly and act as a substrate for the fiber mirror. This concept requires precise control over the length of the fiber pieces and advanced splicing techniques with low losses and negligible mode deterioration. In their work, all used fibers with different outer diameters complicating the handling of the fiber mirrors. In this thesis, it has been tried to produce an assembly of equally sized fibers with 125 μm diameter. Further, elaborate ways of length control and fiber splicing have been investigated, enhancing the quality of fiber lens based mode-matching optics.
Based on the specific application, one requires fiber mirrors of different radii of curvature and diameter. To implement state-of-the-art fiber mirror production techniques in our research group, a new versatile laser ablation setup has been built. This allows the production of ultra-smooth mirror surfaces with much larger range of radii of curvature and diameters compared to the old one.
Further, a new assembly setup for fiber cavities has been realized. This setup is used for fabricating and characterizing cavities for the FCQED experiment of this research group.
With the given advantages, fiber Fabry-Perot cavities are used in numerous applications, e.g. in our photon storage and retrieval experiment or in quantum repeater nodes. By efficiently interfacing almost any emitter, they are also expected to improve the performance of single-photon sources and quantum memories. Apart from quantum information, numerous possible fields of application can be listed, e.g. spectral filtering of light or cavity enhanced spectroscopy.
In the following chapter, theoretical fundamentals of fiber Fabry-Perot cavities will be presented.
To give a full picture of the fabrication process of mode-matched optical fiber cavities the procedure of fabricating mirror surfaces is described in chapter 3. There, the principle of laser ablation and the production setup is explained. Further, a surface reconstruction method and obtained cross-sections of a processed fiber are shown.
Chapter 4 deals with the assembly of cavities for our experiment from the retrieved fiber mirrors. Here, the cavity design and its specific production procedure are introduced. It is followed by a description of the technique to retrieve information about the coupling and the finesse by resonance observation.
In the last chapter, the procedures to enhance the spatial mode-matching between fiber and cavity mode are presented.
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ABSTRACT »
