Polarization independent freeform color router for subwavelength-pixel CMOS image sensors

We proposed the structural symmetry in a freeform color router design for subwavelength-pixel Bayer image sensors to insure the polarization independence as well as the symmetric field profiles. Although the reduced degrees-of-freedom lowers color routing efficiency compared to non-symmetric structures, it still outperforms the conventional color filtering approach. Numerical simulation confirmed that the proposed symmetric color router design for 0.5um-pixel Bayer sensor can achieve the peak optical efficiencies of ~0.8 for red and blue, ~0.7 for green regardless of the polarization direction (corresponds 3.2 times and 1.4 times enhancement over the ideal color filters). We believe that this study presents a more practical and efficient way to design color routers for CMOS image sensor applications.