一般以化學蝕刻法(chemical etching)製作應用於光纖通訊上之單錐度透鏡光纖(tapered fiber)，具有製作簡易快速、成本低廉的優點。不過以此方式所製作的透鏡光纖會因為光纖的光場與雷射不匹配，造成耦光的效率偏低。本研究主要針對光場不匹配的問題而提出一新式雙階段化學蝕刻法(Two steps chemical etching)，利用傾斜角度改變與旋轉蝕刻程序，可在光纖端面製作出x軸、y軸具有不同θx與θy錐角的光纖尖錐，經由熔燒後製作出在x軸、y軸方向上具有不同曲率半徑、能匹配雷射光場的雙錐度透鏡光纖。
具有橢圓狀曲率半徑的雙錐度透鏡光纖，其尖端透鏡可藉由實驗參數的改變而控制x、y軸曲率半徑比率。在同樣的製作時間下，實驗對照組之一般單錐度透鏡光纖耦光效率為30%，雙錐度透鏡光纖耦光效率達到62%，證明以新式雙階段蝕刻法所製作之雙錐度透鏡光纖具有提升耦光效率的效果。對於製作透鏡光纖應用在光纖通訊上，此方法增加了化學蝕刻法更高的實用性。

Chemical etching technique is commonly used to design the tapered fiber that is applied to the optical fiber communication since it is simple, efficient, and inexpensive. However, the tapered fiber made by this technique can cause low coupling efficiency due to the mismatch between the fiber’s mode field and laser. The current study aims to propose a new technique called two steps chemical etching technique to solve the mode field mismatch problem. This new technique utilizes the change of gradient and the rotate etching process to design fiber tips with different θx and θy cone angles on the end of the optical fiber. Moreover, this new technique, through melting, can produce different radius of curvature on both x and y axes of the lens fiber with two tapers to match the laser mode filed.
By changing the experiment parameter, the researcher can control the ratio between x and y axes’ radius of curvature of the lens fiber. With the same fabricating time, the coupling efficiency of the tapered fiber in a control group was 30% while the coupling efficiency of the lens fiber with two tapers was up to 62%. The result indicated that the lens fiber with two tapers made by the two steps chemical etching technique could increase the effects of the coupling efficiency. This technique also enlarges the practicability of the chemical etching technique with respect to designing the tapered fiber used in the optical fiber communication.

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