Polarization control and measurement with meta-optics

Abstract

Metasurfaces are artificially engineered arrays of subwavelength phase-shifting elements which, if designed with explicit polarization dependence, provide a fascinating platform for new polarization optics. In this thesis, we present metasurface diffraction gratings designed to produce arbitrarily specified polarization states on a set of defined diffraction orders, given that the polarization of the incident beam is known. The metasurface diffraction gratings are designed using gradient-descent optimization, followed by a metasurface specific optimization scheme. We also design and implement a metasurface grating that, when used in the reverse configuration, may be used as a parallel snapshot polarimeter, requiring minimum of standard bulk polarization optics. We demonstrate its use in measuring partially polarized light, and show its performance compares favourably with a commercial polarimeter: for the degree of polarization (DOP) measurements we observed a standard deviation of [sigma]= 1.6% and a mean difference of [mu] = 0.6%, and for the state of polarization (SOP) parameters azimuth [chi] and ellipticity [epsilon], we observe standard deviations of [sigma]= 1.320 and [sigma]= 0.43' respectively. This work is of potential interest in any application requiring compact, lightweight and low cost polarization dependent optics, polarization sensing, or polarization imaging.