串接式大角度光功率分離器之研製

Abstract

本實驗旨在研製波長1.55μm與0.6328μm兩種光源下之串接式大角度光功率分離器。光功率分離器的波導結構由對稱式Y形分支波導構成，而爲了有效縮減元件尺寸，Y形分支中的彎曲波導部份以簡式同調耦合的結構設計之。製程上採用鋅鎳為共同擴散源製作光波導，觀察此波導量測結果，並無鋰離子外擴散情況，且有助於光場的侷限性。實驗結果顯示兩種光波導的傳輸效率皆高於80%，而最大輸出分支不均勻率皆低於0.5 dB。依據簡式同調耦合的理論，本研究設計之彎曲區段依序為0.5°、1.5°、2.5°、3°、2.5°、1.5°、0.5°，在此結構下可使研製波長1.55μm的元件，其輸出端之波導距離為 119μm，而研製波長0.6328μm的元件，其輸出端之波導距離為53μm。最後本研究利用兩種彎曲結構模擬此光功率分離器，發現採用簡式同調耦合結構的元件其傳輸率皆相對S形結構高出10%，說明本實驗採用的彎曲結構，除了縮減元件的尺寸外，也相對提高了元件的傳輸率。

Cascaded wide-angle optical power splitters operating at 1.55μm and 0.6328μm are demonstrated. The splitter is essentially a symmetric Y-junction waveguide. To reduce the device length, the bending structure of the Y-junction is replaced by simplified coherently-coupled waveguide segments. Moreover, zinc and nickel co-diffused lithium niobate (Zn-Ni:LiNbO3) waveguide, free of lithium outdiffusion, is used to improve the confinement of optical field. The measured transmission efficiencies are more than 80% and the maximal imbalances are less than 0.5 dB at both wavelengths. The distances between the closer two output waveguides are 119 μm and 53 μm at 1.55 μm and 0.6328 μm, respectively, when the bending angles of the segments are designed as 0.5°, 1.5°, 2.5°, 3°, 2.5°, 1.5°, and 0.5° according to the simplified coherent coupling (SCC) theory. Moreover, simulation results show that the power transmission efficiency of an SCC splitter is 10% higher than that of an S-bend one.