氧化鋁陶瓷包覆之摻鈦藍寶石晶體光纖研製

Abstract

摻鈦藍寶石為一種常見的光源和雷射應用材料，而單模態光纖高功率元件是許多應用的關鍵。利用雷射加熱基座長晶法長出直徑約30 μm的單晶，再以奈米等級氧化鋁粉作為原料，並使用高效和具有成本效益的融膠凝教法製作陶瓷氧化鋁纖衣，再用高達1750 ℃加熱燒結並成功長出單晶氧化鋁。 以固態生長法長出的單晶氧化鋁層在(1-1 0)方向最高達110 μm厚度，而在(0 0 1)方向達40 μm，燒結時間為24小時。以電子背向散射儀量測發現單晶氧化鋁誘發出和纖心相同的取向，而外層多晶則成不規則取向。 實驗室製作出摻鈦藍寶石，其鈦離子濃度0.049 wt%。氧化鋁包覆摻鈦藍寶石晶纖折射率差約4×10-4~5×10-4，操作在波長1550 nm以上可達單模態輸出，操作在780 nm以上則可達少模態輸出，因為晶軸方向不同操作模態稍有差異。晶纖傳輸損耗高達4.7 dB/cm，原因為固態生長單晶層仍有些許孔洞，孔洞在數百奈米等級大小之間，所以會在纖心和纖衣界面處造成大量散射損失。

Ti3+:Al2O3 is a common source of light and laser applications, and high-power active single-mode fiber devices is the key to many applications. Single crystal with a diameter of about 30 μm was grown by laser heated pedestal growth method. Alumina powder was prepared from nano-grade alumina powder using high-efficiency and cost-effective sol-gel method. Up to 1750 ℃ sintering and the successful growth of single crystal alumina.

The single crystal alumina grown by solid state method was grown up to 110 μm in the (1-1 0) direction and 40 μm in the (0 0 1) direction, and the sintering time is 24 hours. It was found by Electron backscatter diffraction technique that single crystal alumina induced the same orientation as that of core, and the outer layer of polycrystal was irregularly oriented. Ti3+:Al2O3 was fabricated in the laboratory with a titanium ion concentration of 0.049 wt%. The refractive index difference of the core and cladding is about 4×10-4~5×10-4, and the single-mode output can be achieved at wavelength above 1550 nm. Few-mode output can be achieved at wavelength above 780 nm, because the crystal axis direction the operating mode slightly different. The measured propagation losses of Al2O3 ceramic-cladded Ti:sapphire single crystal fiber is up to 4.7 dB / cm, because the scattering losses due to pores on the interface between the core and solid state single crystal layer, the size of pores is about hundreds of nanometers.