應用導模共振光柵結構提升稀土奈米粒子 之上轉換螢光訊號

本論文藉由一維導模共振光柵結構(resonance waveguide grating,RWG)的導模共振效應(guided mode resonance, GMR)提升上轉換螢光材料(up conversion)的螢光輸出，這類型的上轉換螢光材料是一種稀土元素(rare Earth, RE)的發光材料，它能夠通過多光子吸收機制將低頻率的激發光轉成高頻率的發射光。整體導模共振光柵結構的組成為:低折射率的SU8光柵層，濺鍍上高折射率材料TiO2 的波導層，最後旋轉塗佈上轉換螢光材料NaYF4:Yb3+,Tm3+的壓克力(poly-methyl-methacrylate, PMMA)薄膜，實驗中將近紅外的激發光和上轉換材料的螢光匹配到導模共振效應的模態，可以產生很強的上轉換材料螢光訊號增益，在激發共振和螢光萃取共振同時發生的條件下，螢光增益可達104 倍，且藉由嚴格耦合波理論(rigorous coupled-wave analysis, RCWA)得知導模共振效應會使TiO2波導層和空氣介面形成局部強場(Strong local field)，使介面激發光電場強度提升進而增強螢光訊號輸出,並藉由導模共振效應特定角度的低穿透、強反射效應，可共振萃取上轉換材料的螢光訊號萃取可近一步的增強螢光輸出。

關鍵字

導模共振光柵；導模共振效應；上轉換螢光材料；局部強電場

並列摘要

Guided mode resonance (GMR) enhanced near-infrared (near-IR) to- visible upconversion fluorescence (UCF) from a rare-earth doped polymer resonant waveguide grating (RWG), comprised of a NaYF4:Yb/Tm nanocrystals doped poly-methyl-methacrylate (NaYF4:Yb/Tm-PMMA) thin layer on top of a textured SU8 substrate with a thin intervening layer of TiO2. Strong UCF is observed by matching either incoming near-IR excitation or out-going UCF extraction to the GMR wavelengths of the rare-earth doped polymer RWG. The intensity of the UCF can be enhanced up to 104 times in visible range and 103 times in near-IR range compared with that from a flat area. According to the rigorous coupled-wave analysis calculations, high enhancement of UCF is attributed to the strong local field generated at the TiO2 waveguide layer due to the resonance between the near-IR excitation light and the GMR. The extraction of the UPF is further promoted when the wavelengths of the UPF resonate with the GMRs.

並列關鍵字

guiding mode resonance ； up-conversion

參考文獻

[9] 楊忠諺 “一維稀土奈米發光材料的合成與鑑定”, Nano communication. 19,24-31 (2012)

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國際替代計量

應用導模共振光柵結構提升稀土奈米粒子之上轉換螢光訊號

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