藉由混成模態耦合之積體光學極化轉換元件

本論文提出一新型積體光學極化轉換器，藉由在波導上覆蓋斜向蒸鍍薄膜，激發波導中的混成模態來達成極化的轉換。斜向蒸鍍薄膜具有傾斜的柱狀結構，光學上呈現雙軸非等向性，藉由鍍膜時改變入射原子的沈積角度，可改變光軸角度與三軸折射率。在極化轉換器的模擬分析上，使用3D全向量有限差分光束傳播法進行計算，可得知光場在通過具有斜向柱狀薄膜為披覆層的光波導時，x方向與y方向電場分佈與功率變化的情形，論文中討論在不同折射率的玻璃基板上，斜向柱狀薄膜對於極化轉換效率的影響，並計算所需的薄膜區長度。討論的斜向柱狀薄膜參數包含：薄膜厚度、柱狀角度、非普極化折射率、及非光學等向性。在最佳化元件參數下，在B270玻璃基板上覆有氧化鉭柱狀薄膜的極化轉換元件，當柱狀薄膜厚度為0.4μm、柱狀角為60°時，可得到高達99.0%之極化轉換效率。由於柱狀薄膜易吸收濕氣而改變其光學性質，影響極化轉換的穩定性，論文中提出在柱狀薄膜表面覆蓋SiO2濕氣阻隔層，以提昇極化轉換的穩定度，當SiO2層厚度為0.3μm、柱狀薄膜厚度為0.4μm、柱狀角為45°時，可得到高達98.71%之極化轉換效率。實驗得到的轉換效率不及模擬所得到的最佳值，其原因為所沈積的柱狀薄膜其三軸折射率與模擬值不同所造成，如能進一步對柱狀薄膜厚度、柱狀角度作最佳化的實驗測試，將能有效提昇極化轉換效率。所提出的創新極化轉換器的元件結構，製作上無須繁雜且昂貴的元件製程，且可應用於任何波導結構中，未來具有廣泛實際應用的潛力。

關鍵字

極化轉換；斜向沉積技術；離子交換波導

並列摘要

In this work, we present a new integrated optic polarization rotator using anisotropic thin film formed by oblique angle deposition as cladding. Obliquely deposited thin film with tilted columnar structure, showing optically biaxial anisotropic. When the column angle varies with the angle of incident atoms, the optical axis angle and the three-axis refractive index can be changed. In the simulation analysis, characteristics of polarization rotator are investigated by 3D full-vectorial finite-difference beam propagation method, calculating the overlap integral between the propagating field and the guided mode, showing x direction and y direction of the electric field distribution and the power variation. We discuss the different refractive index of glass substrate and obliquely columnar thin films for polarization conversion efficiency and the length of thin film region. The columnar film parameters including: film thickness (t), column angle (θ), extraordinary and ordinary indices (ne and no), and optical anisotropy (Δn). The optimal parameters in B270 glass substrate with the Ta2O5 oblique columnar film of thickness 0.4μm and column angle 60° has a conversion efficiency of 99%. Because of the columnar films easily absorb moisture and change the optical properties of the thin film, affecting the stability of the polarization conversion. We propose the SiO2 moisture barrier coating to enhance the stability of the polarization conversion with the 0.3μm thickness of the SiO2 layer, columnar film thickness of 0.4μm, column angle of 45° has a conversion efficiency of 98.71%. In comparison with the experimental conversion efficiency and the simulation values, there are different between simulation values and three-axis refractive index of columnar films. The polarization conversion efficiency could be enhanced by testing the columnar film thickness and the columnar angle. The innovative structure of the polarization rotator, produced on various waveguide structures to achieve polarization rotation and without expensive and complicated process.

並列關鍵字

Polarization converter ； Obliquely deposited technology ； Ion-exchanged waveguide

參考文獻

[1] H. Fukuda, K. Yamada, T. Tsuchizawa, T. Watanabe, H. Shinojima, and S. i. Itabashi, “Polarization rotator based on silicon wire waveguides,” Opt. Express, vol. 16, no. 4, pp.2628-2635, 2008.

[3] K. Merterns, B. Scholl, and H. J. Schmitt, “Strong polarization conversion in periodically loaded strip waveguides,” IEEE Photon. Tech. Lett., vol. 10, no. 8, pp.1133-1135, 1998.

[4] Z. Huang, R. Scarmozzino, G. Nagy, J. Steel, and R. M. Osgood, “Realization of a compact and single-mode optical passive polarization converter,” IEEE Photon. Tec. Lett., vol. 12, no. 3, pp.317-319, 2000.

[6] J. Zhang, M. Yu, G.-Q. Lo, and D.-L. Kwong, “Silicon-waveguide-based mode evolution polarization rotator,” IEEE J. Sel. Top. Quantum Electron., vol. 16, no. 1, pp.53-60, 2010.

[7] D. M. H. Leung, B. M. A. Rahman, and K. T. V. Grattan, “Numerical analysis of asymmetric silicon nanowire waveguide as compact polarization rotator,” IEEE Photon. J., vol. 3, no. 3, pp.381-389, 2011.

國際替代計量

藉由混成模態耦合之積體光學極化轉換元件

未授權

主題瀏覽