非對稱性長週期光纖光柵之製法及其光學特性

Asymmetric corrugated Long Period Fiber Grating Fabrication and their Optical Characterization

陳禎祐(Chen-You Chen)

指導教授 ： 王倫

國立臺灣大學/電機資訊學院/光電工程學研究所/碩士(2007年)

https://doi.org/10.6342/NTU.2007.00438

摘要

先前本實驗室所提出的鋸齒狀光纖光柵 (corrugated fiber grating) 克服了傳統上大多需要感光光纖才能來製作長週期光纖光柵 (LPFG) 的限制。此外，鋸齒狀光纖光柵更表現出對於光共振性質和耦合強度的可調性。雖然鋸齒狀光纖展示出優於傳統光纖光柵的特點，但在以往利用熱蒸鍍金屬膜的方式仍然有許多的不便而且效率也不高。因此一種利用微影製程在光纖上製作鋸齒狀結構的方法於2006年七月提出。本論文承襲此種製作方式，並利用在半導體產業廣為利用之V-凹槽(V-groove)圖案來協助製作。方式為將光纖置於V-凹槽中，並利用負光阻SU8完全擋住氫氟酸蝕刻其下半部，而光纖的上半部再利用半導體製程製作出週期性結構，進而做出非對稱性之鋸齒狀光纖光柵。除此之外，針對此種製程為了增加非對稱性之鋸齒狀光纖光柵之結構強度及良率，本論文也利用三層蝕刻的方式取代一般的蝕刻方式。
除了先前證實的光學特性之外，此種非對稱性鋸齒狀光纖光柵在受到應力的情形之下，會因為結構的非對稱使得兩個不同波長的光由纖核模態(core mode)耦合到具有兩個互相垂直的極化方向低階纖殼模態(cladding mode)，我們利用極化分析儀以及光譜分析儀可以看到這個現象。
此種微影製程的方法製作出非對稱性鋸齒狀光纖光柵，除了其獨特光學特性，我們也進一步對其極化特性作研究，相信在光纖通信和光纖感測兩領域的應用上深具潛力。

關鍵字

長週期光纖光柵 ； 非對稱鋸齒狀光纖光柵 ； SU8

並列摘要

The prior proposed corrugated fiber gratings overcome the limitation of conventional fabrication methods which is most cases require photosensitive fiber for making conventional long period fiber gratings. Besides, the corrugated structures enable the flexibility of tuning coupling strength and resonant conditions. However, making a corrugated structure on a fiber by thermal coating is not convenient and inefficient. Hence, a new lithography method was proposed in July 2006. To this thesis contains the previously proposed lithography method, but take advantage of V-grooves which are commonly used in the industry. We set a fiber in a V-groove and coat it with negative photoresist SU8 to protect the bottom of fiber. Then we make a periodic structure on the top of fiber. To finalize the fabrication of a asymmetric corrugated fiber grating. Besides, we use 3-layer etching method to improve the strength gratings and yield of fabrication of fiber.
In addition to proving the tunable optical properties, The asymmetric corrugated fiber grating is found capable of coupling two wavelengths from core mode to cladding modes of two orthogonal polarization states when a mechanical force is applied. We use a polarization analyzer and an optical spectrum analyzer to characterize this phenomenon.
Asymmetric corrugated fiber gratings made by employing the lithographic method exhibits unique optical characteristics. According to our analysis, it is believed that such fiber gratings may find may applications in optical fiber communication and fiber sensing.

並列關鍵字

Long period fiber grating ； asymmetric corrugated fiber grating ； SU8

參考文獻

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