- 學位論文
高效率及低閥值摻鈦藍寶石晶體光纖雷射
High Efficiency and Low Threshold Laser Source Using Ti:sapphire Crystal Fiber
摘要
摻鈦藍寶石晶體為具有寬廣之螢光頻譜的材料，且其中心波長760 nm對於生物組織的散射損耗及水的吸收較小；故常製作成鎖模雷射或可調式波長雷射，並應用於生物影像系統之光源。使用雷射加熱基座長晶法生長摻鈦藍寶石單纖衣晶體光纖，其纖心直徑為20 μm，外徑直徑為320 μm。單晶光纖可藉由退火方式解決鈦離子之氧化問題，並在最高溫1600 °C 下持溫時間18 小時擁有最佳的晶體品質；其品質因素經量測計算後為257，並可經由計算得知其晶體缺陷之比例約為0.09%。藉由量測螢光生命週期可以推算其晶體光纖腔內之溫度。在低瓦數幫浦下其螢光生命週期約為3.05 μs，並在高瓦數幫浦下略微下降至2.95 μs，換算成溫度則從34 °C 略微上升至40 °C。藉由量測可以得知其對於訊號光之傳輸 損耗為0.075 dB/cm。 以532 nm 綠光倍頻固態雷射幫浦不同穿透率之輸出耦合鏡的腔外式摻鈦藍寶石晶體光纖雷射，並利用模擬對於所量測到的結果進行擬合。經由模擬可以得到所生長的摻鈦藍寶石晶體光纖其吸收截面積為5.2x10-20 cm2，放射截面積為2.4x10-19 cm2。對於532 nm 綠光倍頻固態雷射幫浦架構，在晶纖長度為15~20mm，輸出耦合鏡之穿透率為20~25%時擁有最佳的雷射輸出功率；對於520 nm綠光半導體雷射幫浦架構，其雷射輸出功率最佳化之條件與532 nm 幫浦系統相同。 針對所生長的摻鈦藍寶石晶體光纖在其端面鍍製光學薄膜，使得晶體光纖內形成雷射共振腔，並以波長532 nm 綠光倍頻固態雷射及波長520 nm 綠光半導體雷射進行幫浦。在使用波長532 nm 綠光倍頻雷射幫浦系統時，其斜線效率可達到22.6%，閥值功率為157.7 mW。在使用波長520 nm 綠光半導體雷射幫浦系統時，其斜線效率可達到25.9%，閥值功率為171.7 mW。
並列摘要
Titanium-Sapphire, as the most common broadband fluorescence material, is known for a wide variety of applications such as tunable laser and mode-locked laser. The central wavelength of Ti:sapphire, 760 nm, lies within a region where there are low tissue scattering loss and low water absorption. Thus, it is commonly applied to a multitude of bio-measurement systems. Ti3+:Al2O3 single-cladding crystal fiber was grown by the laser-heated pedestal growth method. It was fabricated with a 20-μm core diameter and 320-μm outer cladding diameter. Annealing methods were used for recovering the Ti3+ ion concentration, and a 1600 °C annealing temperature for 18 hours showed the best crystal quality. The measured figure of merit is 257, and the proportion of crystal defects is estimated to be 0.09%. The temperature of crystal fiber inner cavity can be figured out by measuring the fluorescence life time. The fluorescence life time is 3.05 μs with low pumping power, dropping a little to 2.95 μs with high pumping power, and its temperature slightly rises from 34 °C to 40 °C. The propagation loss of crystal fiber for signal was measured as 0.075 dB/cm. The external cavity Ti:sapphire crystal fiber laser was pumped by a 532-nm laser with different transmittance output couplers, and the experiment results were then fitted by simulation. The following conclusions can be drawn through simulation: the absorption cross section is 5.2x10-20 cm2, and emission cross section is 2.4x10-19 cm2 for our homemade Ti:sapphire crystal fiber; for 532-nm laser pump system, the optimum laser performance is reached when the fiber length is between 15 and 20 mm and the transmittance of output coupler is between 20% and 25%; for 520-nm laser pump system, the condition for optimum laser performance is the same as 532-nm laser pump system. The laser cavity was set up by coating the optical thin film on the surface of Ti:sapphire crystal fiber, and using a 532-nm frequency-doubled solid state green laser and a 520-nm green diode laser to pump it. With 532-nm laser pumping, the slope efficiency can reach 22.6%, and the threshold is 157.7 mW, while the slope efficiency is 25.9%, and the threshold is 171.7 mW with 520-nm laser pump.
參考文獻
延伸閱讀
- Lin, Y. C. (2022). 超寬頻掃頻摻鈦藍寶石晶體光纖雷射研究 [doctoral dissertation, National Taiwan University]. Airiti Library. https://doi.org/10.6342/NTU202203086
- 周志賢（2011）。準相位匹配鉭酸鋰高效率寬頻藍光雷射晶片之研製〔碩士論文，國立臺灣大學〕。華藝線上圖書館。https://doi.org/10.6342/NTU.2011.03120
- 許祐維（2019）。可調波長摻鉻釔鋁石榴石晶體光纖雷射之研究〔碩士論文，國立臺灣大學〕。華藝線上圖書館。https://doi.org/10.6342/NTU201901410
- 羅家堯、周采璇、黃升龍（2007）。高效率摻釹釔鋁石榴石晶體光纖雷射。科儀新知，(158)，24-29。https://doi.org/10.29662/IT.200706.0003
- 陳園迪、劉祥益、洪育維、劉祥麟（2022）。Laser-assisted Rapid Polishing Technology for Silicon Carbide Wafers。機械工業雜誌，(467)，15-21。https://www.airitilibrary.com/Article/Detail?DocID=P20171221002-202202-202202110008-202202110008-15-21