Department of Microelectronics, Fudan University, Shanghai, PR China.
Lab Chip. 2010 Sep 21;10(18):2387-93. doi: 10.1039/c005071g. Epub 2010 Aug 10.
We report a two-dimensional (2D) tunable liquid gradient refractive index (L-GRIN) lens for variable focusing of light in the out-of-plane direction. This lens focuses a light beam through a liquid medium with a 2D hyperbolic secant (HS) refractive index gradient. The refractive index gradient is established in a microfluidic chamber through the diffusion between two fluids with different refractive indices, i.e. CaCl(2) solution and deionized (DI) water. The 2D HS refractive index profile and subsequently the focal length of the L-GRIN lens can be tuned by changing the ratio of the flow rates of the CaCl(2) solution and DI water. The focusing effect is experimentally characterized through side-view and top-view image analysis, and the experimental data match well with the results from ray-tracing optical simulations. Advantages of the 2D L-GRIN lens include simple device fabrication procedure, low fluid consumption rate, convenient lens-tuning mechanism, and compatibility with existing microfluidic devices. We expect that with further optimizations, this 2D L-GRIN lens can be used in many optics-based lab-on-a-chip applications.
我们报告了一种二维（2D）可调谐液体梯度折射率（L-GRIN）透镜，用于在离轴方向上实现光的可变聚焦。该透镜通过具有二维双曲正割（HS）折射率梯度的液体介质聚焦光束。折射率梯度通过两种具有不同折射率的流体（即氯化钙溶液和去离子水）之间的扩散在微流控室中建立。通过改变氯化钙溶液和去离子水的流速比，可以调节 2D HS 折射率分布，从而调节 L-GRIN 透镜的焦距。通过侧视和顶视图像分析对聚焦效果进行了实验表征，实验数据与光线追踪光学模拟结果吻合较好。2D L-GRIN 透镜的优点包括简单的器件制造工艺、低流体消耗率、方便的透镜调节机制以及与现有微流控器件的兼容性。我们期望通过进一步优化，这种 2D L-GRIN 透镜可以应用于许多基于光学的片上实验室应用。
