拉锥空芯光纤的亚波长级微流控光学研究

Optofluidics is a new interdisciplinary field which is developed through the fusion of photonics, optoelectronics and microfluidics. It relates to various research areas including microfabrication and nanofabrication, chemical analysis, biomedicine, adaptive optics, novel lasers, optoelectronic devices and new energy. One of the important research platforms of optofluidics is “lab-on-a-chip”, however, with the development of fiber optical technology, another platform of optofluidics “lab-on-fiber” has attracted widespread attention, which could provide a special way to investigate optofluidics. Now it has become an active research area with great application potential. In this proposal, approaches of tapering various hollow-core fibers to subwavelength-scale have been proposed and investigated such as tapering hollow-core microstructured optical fiber. The cladding of the microstructured optical fiber is composed of a periodic distribution of micrometric air holes running uniformly along the fiber length..The effective refractive index of the cladding is very close to that of air, so it provides largest refractive index contrast between the liquid core and the cladding. Light is confined in the subwavelength-scale liquid core tightly even if the refractive index of the liquid is quite low. Light energy with more than 90% is distributed in the subwavelength-scale core, and the interaction length between light and the liquid sample could be very long with low propagation loss. What’s more, light can be coupled into the subwavelength-scale liquid core with high efficiency because we can fabricate adiabatic transmission area in the liquid-core fiber. In this proposal, we not only provide innovative methods to explore the finest dimension for light guiding in the microfluidics and nanofluidics, and also set up a novel platform for various applications such as measurement of very small amount of fluids and low threshold microfluidic lasers.

微流控光学是光子学、光电子学与微流控技术相结合的一门新兴交叉学科。其研究领域涉及微纳制造、化学分析、生物医学、自适应光学、新型激光、光电子器件和新能源等不同学科及应用。微流控光学的一个重要研究平台是芯片实验室，然而，随着光纤技术的创新发展，光纤实验室，即以光纤为平台的微流控光学研究得到了广泛关注，它提供了一种研究微流控光学的新思路，已成为光纤光学一个极富应用潜力和活力的研究方向。本项目提出独特的拉锥空芯光纤方案，例如微结构光纤包层由空气孔和玻璃微纳结构组成，其有效折射率接近空气，提供了最大可能的液芯与包层折射率差。即使是亚波长级低折射率微纳流体，光也能90%以上束缚在液芯中，而且提供低损耗长距离的波导结构，通过液芯的渐变拉锥区可将激光高效耦合入亚波长尺度液芯中。本项目不仅在探索微纳流体光传输最小尺度方面有创新性，也为极微量流体检测和低阈值微流激光等应用提供了新平台。

光流控技术以其微量样品消耗、高灵敏度、快速响应和光-流体相互作用等优点被广泛应用于生物分析、化学合成、粒子捕获等方面。微结构光纤可将光与液体同时束缚在中空纤芯内，通过纤芯高能量占比、长作用距离等固有优势，为光流控应用提供高效的平台；而亚波长尺度纤芯通过减少模场面积，可有效降低非线性效应阈值。我们研究了亚波长尺度拉锥液芯光子晶体光纤的光流控特性及其应用，光纤型狭缝光波导的光流控特性及拉曼散射效应，亚波长尺度微流控混合光纤的高效耦合，纳米孔光纤布拉格光栅传感器等，证明了亚波长级微结构光纤在光流控领域中的独特优势。这些研究为亚波长量级液芯光纤的设计、制备与实际应用提供了有力的指导，对光流控器件、光纤传感、非线性光学等领域的发展起到了重要的推动作用。