Information advantage from polarization-multiplexed readout of nanophotonic scattering overlay sensors

Nanophotonic structures are powerful tools for sensing, with the goal of retrieving parameters accurately at maximum speed and minimum photon budget. As information on those parameters can be distributed over multiple output scattering channels that propagate to the far field, considering well-chosen combinations of far-field optical degrees of freedom could benefit measurement precision. We explore how multiplexing readout across different polarization channels enhances parameter retrieval in nanophotonic overlay sensors. We measure the relative position between layers with nanoscale scattering structures, known as overlay in semiconductor metrology, and show that multiplexing either incident or analyzed polarization leads to improved parameter retrieval in the systems studied. At fixed photon budget, we extract additional information equivalent to more than 7 dB in signal level. These results demonstrate that significant advantages in measurement performance of nano-optical sensors can be gained by exploiting the vectorial nature of optical fields.