Achromatic micropolarizing filters for visible circular polarization bio-imaging

In this paper, we present a bio-inspired achromatic micropolarizing filters for extracting both right-handed and left-handed circularly polarized components of visible light. By assembling two patterned retarder layers with different retardations, the whole structure behaves as a patterned broadband quarter-wavelength retarder (QWR) across the whole visible spectrum with an overall mean square error (MSE) less than 0.01. Compared with previously reported micro-patterned circular-polarizing devices which only work for a very narrow spectrum band, the strict monochromatic requirement for the light source is completely removed. In addition, promising circular polarization-based imaging is made possible for the whole visible spectrum, enabling a wide range of bio-imaging applications, such as skin cancer diagnosis, biopsy and optical coherence tomography (OCT) imaging.