Nanojet-based dielectric multi-material color splitters for image sensor applications

In this work we have developed new type of color splitters, which separate spectrally and spatially the light reaching image sensors by exploiting the nanojet (NJ) beam phenomenon. The goal is to channel respective R, G and B (red, green and blues) spectra to corresponding pixels, and to replace absorbant color filters for a better light efficiency management. The proposed method relies on light diffraction on the edges of constitutive parts of the studied multimaterial elements. Diffraction of light on the edge of a dielectric microstructure forms a tilted focused beam whose characteristics depend on the ratio of refractive indexes between the materials of the elements creating this edge. Combination of two or more dielectric materials with different refractive indexes leads to the creation of multiple NJs with different angles of deviation, lengths and intensities. The possibility to split color-bands of the incident light by combining two or more dielectric materials is discussed. In this way the generated NJ beams create a spectrally dependent NJ pattern in the near zone. We demonstrate that the proposed topologies of multi-material microlenses help to reduce the size of the color splitting element as well as the optical crosstalk through the dielectric layer.