将石英裸光纤植入聚二甲基硅氧烷基片的微流道中,采用沿光纤轴向光抽运、消逝场激励染料分子的方式,在基片微流道中获得均匀的荧光辐射.实验发现,荧光辐射的强度随光纤轴向距离的增加而衰减,光纤包层溶液折射率越大,荧光沿光纤轴向的衰减越突出;包层溶液中染料浓度越大,荧光沿光纤轴向的衰减也越突出;通过选择适当的包层溶液折射率以及染料浓度可以获得沿光纤轴向接近均匀的荧光辐射.用消逝波激励荧光的辐射理论计算了荧光光强沿光纤轴向的变化,计算结果与实验符合较好.在此基础上,设计并制作了一种具有三个通道的聚二甲基硅氧烷基片,通过在三个微流道中分别注入染料浓度均为0.1 mmol的罗丹明640、罗丹明B及罗丹明6 G的乙醇染料溶液,采用沿光纤轴向消逝波光激励方式,在一块聚二甲基硅氧烷基片上同时实现了三个不同波段的荧光辐射.
A bare quartz optical fiber is implanted in a microfluidic channel of polydimethylsiloxane (PDMS) substrate. Pumping the microfluid by a continuous wave laser with a wavelength of 532 nm along the fiber axis, the fluorescent spectra from the channel filled with lower refractive index (RI) dye solution are obtained. Due to the fact that the evanescent field of the pump beam is homogeneous around fiber, the fluorescent emission from the rim of fiber is uniform. It is found experimentally that the fluorescent emission intensity decreases with the axial distance of fiber, and the intensity is very sensitive to the RI of the dye solution and the dye concentration. For the dye solution with a large RI, the emitted fluorescent intensity attenuates along the fiber axis more obviously than that of the dye solution with a small RI. For the high dye concentration solution, the emitted fluorescent intensity attenuates along the fiber axis also more significantly than that of the low dye concentration solution. Therefore, it is possible to obtain a uniform fluorescence radiation along the fiber axis by selecting a suitably smaller RI and a lower dye concentration solution. The observed experimental phenomena are well explained based on the mechanism of evanescent wave pumping fluorescent radiation. Based on the features of fluorescent emission in the microfluidic chip, a PDMS chip with three micro-channels is designed and fabricated. After injecting ethanol solutions of rhodamine 640, rhodamine B and rhodamine 6 G separately into the three channels and pumpingthese solutions by evanescent wave along the optical fiber axis, three fluorescence emissions with different wavelength ranges are successfully observed in a single PDMS chip.