Tunable Liquid Gradient Refractive Index Lens

4 Tunable Liquid Gradient Refractive Index Lens 

All the in-plane tunable microlenses discussed to this point are classical refractive types. Mao et al. reported a tunable microlens configuration based on a liquid gradient refractive index (L-GRIN) lens mechanism [20]. 

More importantly, with precise microfluidic manipulation, one can change both the focal disfance of the L-GRIN lens by adjusting the refractive index contrast (difference between maximum and minimum in the gradient) and also the direction of output light by shifting the optical axis [20]. 

Ray tracing experiments to characterize variable focal length of and light intensity after combination of air-water-interface lens and PDMS lens at different flow rates of D1 water, (a) 0 pL/ min. (b) 10 pL/min. (c) 20 pL/min. (d) 30 pL/min. (e) 40 pL/min. (f) Intensity plots along white lines depicted in (a) through (e). Solid curves are fittings to experimental data. (Source Shi, 

Takiguchi, T. Odake, M. Ozaki, T. Umemura, and K.I. Tsunoda, Liquid/ liquid optical waveguides using sheath flow as a new tool for Uquid/Uquid interfacial measurements, Applied Spectroscopy, vol. 57, pp. 1039-1041,2003. 

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