短波紅外線螢光粉調控及其於光纖放大器與發光二極體之應用

Abstract

短波紅外線因其獨特性質，於不同領域具高應用潛力。於固態照明中，螢光粉轉化發光二極體已為現今常見之光源，且短波紅外線螢光粉亦可應用於此類發光二極體，且具可調控放光波段之優勢，為短波紅外線光源提供另一選擇。然短波紅外線螢光粉應用於光纖放大器之應用仍待發展與研究。故於本研究中，將探討短波紅外光螢光粉之調控與其應用於光纖放大器與發光二極體。 本研究中前半(Chapters 3 and 4)部分，著重短波紅外線螢光粉之合成與分析研究，且將最佳條件之螢光粉進行晶體光纖之生長，評估其應用潛力。因現今商用Y3Al5O12:Cr4+晶體光纖無法調整Cr4+之濃度導致其發光強度受限，故其一(Chapter 3)為Y3Al5O12:Cr3+/4+,Ca2+,Mg2+，藉Cr離子濃度調整與二價陽離子摻雜，最佳化Cr4+之放光表現，且所生長之晶體光纖於短波紅外線之放光強度，高於商用Y3Al5O12:Cr4+商用晶體光纖。此外，晶體光纖研究領域之材料多樣性受局限，故其二(Chapter 4)為開發全新晶體光纖系統(Ga,Ge)2O3:Cr3+,Ni2+，藉Cr3+與Ni2+雙活化劑摻雜與Ge4+摻雜進行價數補償。因Cr3+得有效能量轉移至Ni2+，故得獲寬譜帶放射峰於短波紅外線之波段。除生長為晶體光纖之應用，因Cr3+可有效藉藍光激發，故此系列螢光粉亦可應用於短波紅外線光源。 本研究後半(Chapters 5 and 6)部分，致力於短波紅外線尖晶石螢光粉之研究，建立有效調控放光波段之策略與延伸放光波段之策略，亦評估其於短波紅外線光源之應用可行性。其一(Chapter 5)為Cr3+與Ni2+雙活化劑摻雜之MgAl2O4–MgGa2O4–Mg2SnO4固態溶液系統，探討尖晶石系統結構轉換於放光性質之影響，且著重探討Cr3+團簇之消長與Ni2+放光波段之調控。將合成之螢光粉進行發光二極體封裝測試，展現其短波紅外線光源之應用示範。其二(Chapter 6)為MgGa2O4:Cr3+,Er3+，藉Cr3+濃度變化探討Cr3+離子團簇於能量轉移至Er3+之影響，並藉Er3+濃度調整得最佳化之放光強度於短波紅外線波段，搭配局部結構與進階光譜分析揭示Cr3+團簇於Er3+放光強度之影響，得改善稀土元素低吸收導致之螢光強度受限窘境。 綜上所述，本研究致力於推動短波紅外線螢光粉之發展，藉系統性之陽離子取代策略、結構調控及能量轉移機制探討，提升螢光粉之放光表現且建立有效調控放光位置之策略，同時藉螢光粉之配方設計思維改良與開發晶體光纖材料，揭示螢光粉於晶體光纖與發光二極體之應用潛力，為短波紅外線螢光粉領域提供嶄新之設計思路與應用方向。

Shortwave infrared (SWIR) phosphors possess high application potential in various fields due to their unique properties. In solid-state lighting, phosphor-converted light-emitting diodes (pc-LEDs) have become common light sources nowadays. SWIR phosphors can also be applied to such pc-LEDs and have the advantage of tunable emission wavelengths, providing another option for SWIR light sources. However, the application of SWIR phosphors in optical fiber amplifiers still needs development and research. Therefore, this study will explore the emission tuning of SWIR phosphors and their applications in optical fiber amplifiers and pc-LEDs. The first half (Chapters 3 and 4) of this study focused on the synthesis and analysis of SWIR phosphors, and crystal fibers were grown using the optimized phosphors to evaluate their application potential. The current commercial crystal fiber faces the challenge of low photoluminescence intensity because of the limited Cr4+ content in commercial Y3Al5O12:Cr4+ crystal fiber. Hence, the first part (Chapter 3) is Y3Al5O12:Cr3+/4+,Ca2+,Mg2+, which optimizes Cr4+ photoluminescence performance through Cr ion concentration tuning and divalent cations doping. The grown crystal fiber shows higher SWIR emission intensity than commercial Y3Al5O12:Cr4+ crystal fibers. Besides, the crystal fiber research field also encounters the challenge of low material diversity. Therefore, the second part (Chapter 4) aims to develop a new material system, (Ga,Ge)2O3:Cr3+,Ni2+, using Cr3+ and Ni2+ co-activators doping for obtaining SWIR emission and Ge4+ doping for charge compensation. Due to effective energy transfer from Cr3+ to Ni2+, a broadband emission peak in the SWIR band is obtained. In addition to crystal fiber applications, since Cr3+ can be effectively excited by blue light, this series of phosphors can also be applied to SWIR light sources. The latter half (Chapters 5 and 6) of this study focused on SWIR spinel phosphor research and evaluated their feasibility for SWIR light source applications. The effective emission tuning strategy and emission range extension method were established. The first part (Chapter 5) is the MgAl2O4–MgGa2O4–Mg2SnO4 spinel solid-solution system doped with Cr3+ and Ni2+ activators, investigating the effects of spinel system structural evolution on photoluminescence properties, with emphasis on exploring the relationship between Cr3+ clusters and Ni2+ emission band tuning. Pc-LED packaging tests were conducted on the synthesized phosphors, demonstrating their potential for application as SWIR light sources. The second part (Chapter 6) is MgGa2O4:Cr3+,Er3+, exploring the effect of Cr3+ clusters on Er3+ through Cr3+ concentration tuning and optimizing emission intensity in the SWIR band through Er3+ concentration tuning. Local structure investigation and advanced photoluminescence analysis are also conducted to reveal the effect of Cr3+ clusters on Er3+ emission intensity, which can overcome the issue of low absorption for rare-earth elements. In summary, this study is dedicated to advancing the development of SWIR phosphors through systematic cation substitution strategies, structural regulation, and energy transfer investigations to enhance the luminescence performance of phosphors and establish effective emission position-controlling strategies. Meanwhile, by developing optical crystal fiber through phosphor design concepts, this work reveals the potential of phosphors in optical crystal fibers and pc-LEDs, providing novel design approaches and directions for the application of SWIR phosphors.