A Study of Elliptical Fiber Microlenses
| Autor: | Szu-ming Yeh, 葉斯銘 |
|---|---|
| Rok vydání: | 2006 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 95 Two new schemes of fiber microlenses for coupling between the high-power 980nm laser diodes and single-mode fibers (SMFs) are proposed. The quadrangular-pyramid-shaped fiber microlens (QPSFM) is fabricated by grinding a quadrangular-pyramid-shaped endface and then through heating in a fusing splicer to form an elliptical microlens endface. In comparison to the traditional wedge-shaped fiber microlens, the QPSFM structure can control two axial curvatures to form an elliptical microlens endface, and then control the aspect ratio of fiber far-field pattern to match the elliptical mode fields of lasers. The coupling efficiency of 83% for the QPSFM has been demonstrated. Another scheme of fiber microlens is the conical-wedge-shaped fiber microlens (CWSFM). The CWSFM is fabricated by grinding a conical-shaped fiber endface, then grinding a pair of wedge planes on the conical-shaped fiber endface, and finally through heating in a fusing splicer to form a good elliptical microlens endface. The coupling efficiency of 84% for CWSFM has been demonstrated. The fabrication of QPSFM requires five-step grinding processes. The range of grinding offset is 0.5~3.0μm, and the average of grinding offset is 1.5μm. The fabrication yield of QPSFM is low due to the large grinding offset. The fabrication of CWSFM requires only three-step grinding processes. The range of grinding offset is 0.3~1.5μm, the average of grinding offset is 0.8μm. The fabrication yield of CWSFM is high due to the small grinding offset. The fabrication yield is about 60% for 70% coupling efficiency; whereas the fabrication yield becomes 96% for 60% coupling efficiency. The laser-to-SMFs coupling of the fiber microlens was modeled based on the diffraction theory. The coupling efficiency, the tolerance of alignment, and the tolerance of fiber microlens offset were calculated according to this model. There is a good agreement between the simulation and the experiment values. In this study, two new scheme of fiber microlenses of the QPSFM and CWSFM with high coupling efficiency have been demonstrated. The CWSFM structure has the benefits of simple process and high yield that is suitable for use in commercial high power laser module. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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