A Novel Two-dimensional Direction Adjustable Liquid Gradient Refractive Index (L-GRIN) Microlens

A tunable two-dimensional (2D) liquid gradient refractive index (L-GRIN) microlens is presented which can be used in adjusting light beam focal point direction in in-plane system in this paper. Finite element method (FEM) can be used to simulation the convection and diffusion process happening in core inlet flow and cladding inlet flow. And the ray tracing method can help us to simulate the focusing effect including focal length and output beam spot size. When the core and cladding liquid types are fixed, by adjusting the concentration of the core inlet liquid or the flow rate of the core and cladding inlet, the simulation result shows the focal length can change from 150 mu m to infinity from the inlet side theoretically. By adjusting the proportion of the symmetric cladding inlet flow rate including Q(right)/Q(left) and Q(up)/Q(down), we get the continuously adjustable focus direction and it is a two-dimensional adjustable direction rather than the line freedom tunable direction. We suppose this kind of flexible microlens can been used in integrated optics and lab-on-a-chip system.