Vortex Retarder Allows Broadband Polarization Direction Indicator

Polarization direction indicator (PDI) by vortex retarder has been proved to be a powerful tool in polarization direction measurement. It features on one-shot, nonmechanical motion and nonelectromechanics and high robustness to random noises. However, as a wavelength-sensitive device and the key component in the PDI, a vortex retarder can only work in single-wavelength mode, which, obviously, poses severe application limitations since most practical polarization direction measurement applications actually require broadband detection. This work is to explore the common concern that if a PDI by vortex retarder can work in broadband or wide-spectrum detection mode. It is the first time to theoretically and experimentally prove that a PDI by vortex retarder can work as a broadband PDI, even across the entire visible wavelength band.