Multi-functional, optofluidic, in-plane, bi-concave lens : tuning light beam from focused to divergent

Abstract

The miniaturization and integration of in-plane micro-lenses into microfluidic networks for improving fluorescence detection has been widely investigated recently. This article describes the design and demonstration of an optofluidic in-plane bi-concave lens to perform both light focusing and diverging. The concave lens is hydrodynamically formed in a rectangular chamber with a liquid core liquid cladding (L 2) configuration. In the focusing mode, an auxiliary cladding stream is introduced to sandwich the L 2 configuration for protecting the light rays from scattering at the rough chamber wall. In the diverging mode, the auxiliary cladding liquid changes its role from avoiding light-scattering to being the low-refractive-index cladding of the lens. The focal length in the focusing mode and the divergent angle of light beam in the diverging mode can be tuned by adjusting the flow rate ratio between core and cladding streams.