School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798.
Lab Chip. 2012 Oct 7;12(19):3785-90. doi: 10.1039/c2lc40442g.
Transformation optics is a new art of light bending by designing materials with spatially variable parameters for developing wave-manipulation devices. Here, we introduce a transformation optofluidic Y-branch splitter with large-angle bending and tuning based on the design of a spatially variable index. Differing from traditional splitters, the optofluidic splitter is achieved in an inhomogeneous medium by coordinate transformation. The designed bidirectional gradient index (GRIN) distribution can be achieved practically by the convection-diffusion process of liquid flowing streams. The transformation optofluidic splitter can achieve a much larger split angle with little bend loss than the traditional ones. In the experiments, a large tunable split angle up to 30° is achieved by tuning the flow rates, allowing optical signals to be freely transferred to different channels. Besides the symmetrical branch splitting, asymmetrical Y-branch splitting with approximately equal power splitting is also demonstrated by changing the composition of the liquids. The optofluidic splitter has high potential applications in biological, chemical and biomedical solution measurement and detection.
变换光学是一种通过设计具有空间变化参数的材料来弯曲光线的新技术，用于开发波操控器件。在这里，我们介绍了一种基于空间变化折射率设计的具有大角度弯曲和调谐功能的变换光流分束器。与传统的分束器不同，该光流分束器通过坐标变换在非均匀介质中实现。设计的双向梯度折射率（GRIN）分布可以通过液体流动的对流-扩散过程来实现。与传统分束器相比，变换光流分束器可以实现更大的分束角，而弯曲损耗较小。在实验中，通过调节流速可以实现高达 30°的大可调分束角，允许光学信号自由地传输到不同的通道。除了对称的分支分束，通过改变液体的组成，还演示了具有近似相等功率分束的非对称 Y 分支分束。该光流分束器在生物、化学和生物医学溶液测量和检测方面具有很高的应用潜力。
