Highly Sensitive Polarization Rotation Measurement through a High-Order Vector Beam Generated by a Metasurface

The precise determination of the polarization state of light is fundamental for a vast variety of applications in remote sensing, astronomy, optics and terahertz technology, to name just a few. Typically, polarization characterization is performed by using a combination of multiple optical devices such as beam splitters, polarizers, and waveplates. Moreover, to achieve high-precision, balanced photodetectors and lock-in amplifiers are employed, thus contributing to increasing system complexity. Here, a technique for polarization rotation measurements with a dynamic range of 180° and a sensitivity of about 10−2 degrees is realized using a properly designed metasurface. Such device generates a vector beam with an azimuthally-dependent polarization distribution, as a result of the superposition of two vortex beams carrying opposite orbital angular momenta (ℓ = ±30). After propagation through a linear polarizer, the spatial intensity profile of such a beam turns into 60 lobes. By tracking the displacement of only two of these lobes on a camera, the rotation of the input polarization state can be retrieved with high resolution. The proposed approach offers a new route toward the development of compact high-precision polarimeters and can also be exploited in quantum information processing, optical communications, as well as nonlinear and chiral optics.