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標題: | 超寬頻淺蝕刻型次波長光柵多模干涉分光器 Ultra-broadband Shallow-etched Subwavelength Grating Multimode Interference Splitter |
作者: | Po-Han Chen 陳柏翰 |
指導教授: | 林恭如(Gong-Ru Lin) |
共同指導教授: | 黃定洧(Ding-Wei Huang) |
關鍵字: | 多模干涉,次波長光柵,淺蝕刻,寬頻,分光器, Multimode interference,subwavelength grating,shallow-etching,broadband,splitter, |
出版年 : | 2019 |
學位: | 碩士 |
摘要: | 隨著近年電腦、行動裝置及智慧型設備日益普及,物聯網、大數據與雲端運算等新型態的網路技術廣泛布局在生活周遭,隨處可見連接上網的窗口,龐大的數據流量因應而生,傳統的網路電纜已不足以面對如此高速與大量的數據處理,人們對於更大的通訊頻寬需求年年遽增,慶幸的是,近年來伴隨著積體電路製程技術的成熟,過去線寬較小且不容易製作的結構設計已可被達成,部分代工廠也投入矽光子元件的開發,並提供學界研究單位晶片下線的機會,因此,以四族矽為主的光電材料發展的矽光子元件優點相繼被發掘,使得在各種高速矽光子元件可在現行晶片系統上作使用,由於低插入損耗、高頻寬等矽光子元件陸續被開發出來,諸多的被動元件透過將光源訊號進行分光、調制與結合等應用下,將錯綜複雜的訊號格式作處理,表現出在訊號傳輸系統上高效能優勢的潛力。
本論文重點在於探討開發低穿透率損耗、大頻寬的多模干涉分光器,以比利時代工廠IMEC M12OTE_FC_4500_25600作為參考及比較對象,先以時域有限差分法 (FDTD) 與特徵模態展開法 (EME),對其評估分光的效能,兩種方法模擬結果下,其穿透率損耗及頻寬分別為0.32 dB、0.23 dB及140 nm、160 nm,驗證不同模擬方法下結果極為接近;隨後提出超寬頻淺蝕刻型次波長光柵多模干涉分光器,結合週期長度為200 nm的次波長光柵週期性結構與兩側150 nm的淺蝕刻平台,透過改變不同佔空比0.4/0.5/0.6/0.7的變化,調整干涉區域之等效折射率,以自我成像理論 (Self-Imaging Theory) 中等效折射率與特徵長度的近似關係,修正不同佔空比下元件干涉區域的長度,藉此達到更佳的輸出穿透率,干涉區域寬度固定為4.5 μm,當佔空比為0.4時,多模干涉分光器長度為21.8 μm,以1-dB的穿透率損耗為標準下,頻寬模擬結果為380 nm,為克服在短波長發生的急劇反射損耗,另外將週期長度縮短至190 nm,多模干涉分光器長度為19.57 μm,頻寬提升為500 nm,完整涵蓋O、E、S、C、L及部分U-Band光通訊範圍,以相同的寬度、更短的元件長度相比IMEC M12OTE_FC_4500_25600頻寬效能,足足達到近3.5倍多的可操作頻寬範圍。 With the tremendous widespread of computers, mobile devices and smart devices in recent years, new types of Internet technologies such as IoT, big data and cloud computing are widely distributed around the world. Demands for much larger data transmission bandwidth are growing year by year. Fortunately, with the highly development of integrated circuit process, previous structural designs with infeasible small line widths can be achieved nowadays. Some foundries are willing to manufacture silicon photonic components for academic customers. Therefore, some of the advantages of the silicon photonic components based on Group-IV materials have been discovered, so that various high-speed photonic devices can be used on the current chip system. Since low insertion loss, high-bandwidth photonic elements have been successively developed, complex signal formats have been processed through many passive components by applying splitting, modulation, and combination of light signals. With the high performance in signal transmission systems, silicon photonics shows great potential for many applications. In this thesis, a multimode interference splitter with low transmission loss and large optical bandwidth has been demonstrated. A standard device M12OTE_FC_4500_25600 was provided by the foundry IMEC in Belgium and used as a reference and comparison subject. The finite difference time domain (FDTD) and the eigenmode expansion method (EME) were used to evaluate the light splitting performance. In the simulation results of these two methods, the transmission loss of 0.32 dB and 0.23 dB and bandwidth of 140 nm and 160 nm are obtained, respectively. It is verified that the simulation results using these two different methods are very close to each other. Subsequently, an ultra-broadband shallow-etched subwavelength grating multimode interference splitter with a periodicity of 200 nm and a slab height of 150 nm on both sides is proposed. To adjust the effective refractive index of the multimode interference region by selecting the duty cycles of 0.4, 0.5, 0.6, and 0.7. Based on the approximate relationship between the effective refractive index and the characteristic length in self-imaging theory, the length of the multimode interference region of different duty cycles is modified. In order to get higher output transmission, the width of the multimode interference region is fixed at 4.5 μm. And the length of the multimode interference region is 21.8 μm at duty cycle of 0.4. Under the criterion of 1-dB transmission loss, the bandwidth is 380 nm according to the simulation result. To overcome the rapid reflection loss at the short-wavelength region, the periodicity is shortened to 190 nm. The length of the multimode interference splitter is 19.57 μm and bandwidth is up to 500 nm, covering the optical communication ranges from O, E, S, C, L to partial U-Band. In comparison with M12OTE_FC_4500_25600, it reaches nearly 3.5 times the operating optical bandwidth under the same width of multimode interference region but a much shorter component length. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/74831 |
DOI: | 10.6342/NTU201904266 |
全文授權: | 有償授權 |
顯示於系所單位: | 光電工程學研究所 |
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