- 學位論文
矽核光纖之製備與分析及其產生矽微米球之應用
Fabrication and analysis of silicon-cored fibers and applications of produced silicon microspheres
摘要
在本論文中，我們將粉末套管法與垂直下拉法做結合來製作單晶矽核光纖(silicon-cored fibers)。我們使用成本便宜許多的多晶矽粉來取代成本高昂的單晶矽棒或晶種來製作矽核光纖。藉由優化抽絲的相關參數後，可以成功製作出長度長達一公尺的矽核光纖。最後抽出來的矽核光纖其尺寸約為玻璃包覆層直徑100-300微米、矽核心直徑10-30微米。由能量散佈分析儀可知製作出的矽核光纖有著高純度的特性。由拉曼、X光散射儀可知矽核光纖有著高度結晶的特性。由背向散射電子繞射儀分析得知其單晶的長度可維持超過100微米。 我們使用以銀為催化劑之溶液形式金屬輔助化學蝕刻法製作抗反射結構在矽核光纖端面之上，量測到的反射率降到2.4% 接近模擬的最低值。在1550奈米工作波段，我們使用雷射融接玻璃光纖和矽核光纖之纖殼可將融接損耗降低至1dB。 當光從矽核光纖傳到單模光纖(大數值孔徑到小數值孔徑)，由於模態不匹配會導致極大之耦合損耗。在本論文中，我們提出製作微透鏡在矽核光纖上來提高耦合效率。 我們採用二氧化碳雷射來加熱矽核光纖中裸露的矽核心來快速製備具有高品質因子(quality factor)迴音廊模態(whispering gallery modes)的矽微米球共振腔(silicon microsphere resonator)。使用玻璃錐狀光纖耦合法來激發在矽微米球上的迴音廊模態，得到的最高品質因子為4 x 10^5。本文中，也藉由熱光效應(thermo-optic effect)來探討關於在矽材料上的共振波長飄移現象。我們使用電弧加熱一段矽核光纖以產生一連串矽微米球，並將矽微米球置入單模光纖和中空光纖融接後的空腔中產生光纖式溫度計，其感溫靈敏度約80pm/℃，最高感溫到700℃。由於其開放空間之架構可和外界環境接觸，該元件可作為其他感測應用。 在微光纖的領域裡，我們從聚合物溶液中可拉出壓克力(PMMA)微光纖陣列並使用聚二甲基矽氧烷(PDMS)封裝。微光纖之端面可以控制到單細胞之尺寸，為了測試該基板是否可應用在單細胞光遺傳學上，我們培養帶有光蛋白之HEK293T細胞在基板上並使用紫外光雷射激發。
並列摘要
Single-crystal silicon-cored fibers were made by using a combined techniques of powder-in-tube and vertical-drawing. Much cheaper polycrystalline Si powders substituting expensive single-crystal Si powders or seed rods were packed into a fused silica tube. By optimizing the drawing parameters, meter-long silicon-cored fibers were obtained. The silicon-cored fibers were drawn with resultant silica cladding and Si core diameters being in the range of 100-300 um and 10-30 um, respectively. According to energy-dispersive x-ray spectroscopy, the fabricated Si core is in high purity. From Raman spectrum and X-Ray diffraction analysis, the silicon-cored fiber is high crystalline. The single crystalline property of silicon-cored fibers could last for more than 100 um according to electron backscatter diffraction analysis. We applied solution based metal-assisted chemical etching method with silver catalyst to create anti-reflection structures on the end surface of a silicon-cored fiber. The measured reflectance of the etched silicon area of a silicon-cored fiber could reach to 2.4 %, approaching the simulated low value. The laser splicing loss was reduced to 1 dB when spliced with a silica fiber for working in 1550nm wavelength. When mode propagating from a silicon-cored fiber to a single mode fiber (high NA to low NA) direction, the large modal mismatch which leads to high coupling loss. Here, we propose a design of fabricating a microlens on Si core with electric arc to increase the coupling efficiency. Silicon microsphere resonators which exhibited high quality factor (Q) whispering-gallery-modes (WGMs) could be rapidly fabricated from silicon-cored fibers using CO2 laser reformation. WGMs were excited by using the tapered silica fiber coupling technique, and a record resonant Q as high as 4 x 10^5 was obtained. The shift of resonant wavelength caused by thermo-optic effect of Si material was also observed. We heated a silicon-cored fiber to produce silicon microspheres sequentially by arc discharges, and a silicon microsphere thus obtained was put in a hollow core fiber spliced with a single mode fiber to form a temperature fiber sensor. The measured thermal sensitivity was ~80pm/℃ for temperature range up to 700℃. With its open cavity structure such an in-line optical fiber sensor may find other sensing applications because of its ability of direct interaction with external environments. In the field of microfiber, arrayed Poly(methyl methacrylate) (PMMA) microfibers were drawn from a polymer solution and packaged with polydimethylsiloxane (PDMS). The exposed end face of packaged microfiber was tuned to have a size corresponding to a single cell. To demonstrate its capability for single cell optogenetics, HEK293T cells expressing channelrhodopsin-2 (ChR2) were cultured on the platform and excited with UV laser.