A new scheme of fabricating the tapered hyperbolic-end fibers (THEFs)microlenses using unique etching and fusion techniques is proposed. TheTHEFs were fabricated by symmetrically tapering the fiber during theetching process and hyperbolically lensing the tip during the fusing process.The tapered hyperbolic microlenses have demonstrated up to 82% couplingefficiency for a laser with an aspect ratio of 1:1.5. The influence of the tapering asymmetry on the coupling has also been investigated
experimentally and theoretically. The axially symmetrical taperedmicrolenses of the THEFs showed that far-field profiles were well approximated to a Gaussian profile, while the asymmetric taper had deviated significantly from a Gaussian profile. A theoretical analysis illuminated a
larger wavefront transformation of the hemispherical microlenses. A lesser phase aberration of the normalized optical path difference (OPD) was found in the hyperbolic-end lens, and that resulted in more than 2 dB improvement
in the coupling efficiency when compared to the currently available hemispherical microlenses. The high-coupling performance of the hyperbolic microlens was due to an improved wavefront matching between the laser and
the fiber, which was one of the most important contributions in this study.The 1.55 µm fiber grating external cavity lasers (FGECLs), packaged with THEF microlens for coupling the fiber grating external cavity, have been investigated for different combinations of coupling efficiency (£b) and Bragg reflectivity (Rg). Various tapered hyperbolic-end fiber microlenses
with different coupling efficiency have been fabricated for this study. The FGL of higher £b = 72% and Rg = 0.52 has a stronger resonant feedback as the spectral output showed a single longitudinal mode with the side-mode-suppression-ratio (SMSR) greater than 45dB, a high output power of greater than 5mW, and a lower threshold current. However, for the case of £b = 68% and Rg = 0.35, the FGL exhibited a more stable SMSR against the variation of pumping current and temperature. Numerical simulations have also been performed on the SMSR at different coupling efficiencies and Bragg reflectivity for the FGLs. The high performance of the FGLs can be achieved through a higher coupling efficiency between a laser diode and a single-mode fiber. The calculated SMSR showed an excellent agreement with the measured data.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0602104-131440 |
| Date | 02 June 2004 |
| Creators | Yang, Huei-Min |
| Contributors | Wood-Hi Cheng, Ching-Ting Lee, Tsong-Sheng Lay, Yan-Kuin Su, Sheng-Lung Huang, Yin-chieh Lai, San-Liang Lee |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | Cholon |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0602104-131440 |
| Rights | not_available, Copyright information available at source archive |
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