Detection of partial polarization of light beams with dipolar nanocubes

We confirm experimentally that the degree and state of polarization of a random, partially polarized electromagnetic beam can be obtained by probing the field with a nanoscatterer. We use a gold nanocube on silicon substrate as a local scatterer and detect the polarization characteristics of the scattered far field, which enables us to deduce the state of partial polarization of the field at the nanoprobe site. In contrast to previous beam characterization methods where spatial resolution is limited by the pixel size of the detector, the accuracy of the current technique is specified by the particle size. Our work is the first step towards polarization-state detection of random optical near fields for which the use of nanoprobes is required.