High Curvature Concave-Convex Microlens

We report in this letter a concave-convex microlens (CCML) consisting of two different high curvature surfaces. Compared with the conventional plano-convex microlenses, the CCML not only allows for more design freedom, but also offers significantly improved optical performance, particularly minimization of aberration, as is critical when the size of optical components is small. Experimentally, focusing capability at different wavelengths was demonstrated, and the axial chromatic aberration was found significantly reduced to similar to 4.6% of the focal length shift under wavelength 450-660 nm.