微米光子回路中能量的荧光显示与调节

基于弯曲的罗丹明B(rhodamine B)掺杂聚合物微米线,搭建了Y型分束器、微米线-环形腔耦合结构等典型微米光子回路;采用锥形光纤耦合的方式,将光能量导入回路并在微米线中激发荧光;通过移动锥形光纤增加光的传输距离,分析能量的输出强度与传输长度之间的关系。研究发现,通过激发出的荧光光路强度,可显示回路中的能量沿微米线轴线周期性地衰减振荡,并在微米线弯折处发生相位跃变;回路输出端能量随传输距离的增加呈周期性变化,且在半个周期内,可将Y型分束器分光比从1.3调节到2.4(<2μm),使耦合结构中单个输出端的强度峰谷比达到2.1(<6μm)。利用锥形光纤耦合激发出的荧光,可在远场直接显示回路的能量传输状态,并在传输距离改变时对能量的耦合情况进行实时反映,实现回路输出性能的大范围调节,为复杂微光子器件的搭建及性能调节提供了一种直观、简便的方法。

Energy Observation and Adjustment of Micro Photonic Circuits

We assemble typical micro photonic circuits based on rhodamine B doped polymer microfibers(RhB doped PMFs),such as Y beam splitter and microfiber-ring cavity coupling structures.Through the tapered fiber,a 532 nm incident light is launched into the RhB doped PMFs and excited the fluorescence simultaneously.The propagation distance of the energy could be increased by moving the tapered fiber along the PMF.We analyze the relationship between the propagation distance and the output intensities of the coupling structures.The results show that the energy distribution in the doped PMF could be visualized according to the fluorescent path in the circuit.Along the straight part of PMF,the energy propagates decreasingly with a periodic oscillation.Significant phase jump could be observed at the curved part.Moreover,the output intensity of the circuit also has a periodic variation with the increasing propagation distance.By simply moving the tapered fiber in a half period,the split ratio of the Y splitter could be adjusted from 1.3 to 2.4(within 2μm)while the peak-to-valley ratio of the output intensity in the ring cavity structure could reach 2.1(within 6μm).For the fluorescence excited by the tapered fiber in the coupling structure,we could directly observe the energy distribution in real-time from optical far field.A large changing range of the output intensity could be realized by simply moving the tapered fiber within a few micrometers.Our results demonstrate a visible and simple approach for photonic circuit fabrication and adjustment.