High-efficiency broadband polarisation converter via patterned multilayer twisted liquid crystal polymer

We propose an ultra-compact polarisation converter based on liquid crystal (LC) material for effectively converting the obliquely incident unpolarised light into horizontal linearly polarised beam within the visible frequency range. Multilayer twisted configuration is introduced here to tackle the inherent dispersion issue from the LC itself and extended Jones matrix is employed to analyse the propagation of the electric field inside the LC medium under possible oblique illumination. Spatial angular separation of orthogonal polarised lights and polarisation conversion into the same polarisation direction are realised through specific patterned structure design, which effectively reduce the thickness of the device without sacrificing performance. Experimental results demonstrated that our fabricated LC-based device can deliver >80% polarisation conversion efficiency at normal illumination and 59%-80.5% efficiency for +/- 10 degrees oblique incidence over the visible spectrum. Therefore, we envision that our presented device might find numerous potential applications associated with polarisation regulation such as vortex beam generator, augmented reality and optical computing.