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

Abstract

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 highprecision, 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.

Optical Metasurfaces for Generation and Superposition of Optical Ring Vortex Beams

“…By controlling the major axis, ellipticity, and handedness of the incident polarization state, we have experimentally demonstrated various superpositions of ring OAM beams, whose intensities are spatially modulated after passing through a polarizer. The unusual properties of the developed metasurface devices are very attractive for many research fields, including polarization measurement, [35][36][37][38] optical communications, optical tweezers (particle rotation), and quantum sciences. [39,40] As an application example, we experimentally demonstrate polarization measurement based on this new technology.…”

Rotational Doppler Frequency Shift from Time‐Evolving High‐Order Pancharatnam–Berry Phase: A Metasurface Approach

“…For the case of linearly polarized light, which can be expressed as a superposition of RCP and LCP light, two vortex beams with opposite topological charges of and are simultaneously generated, giving rise to a vector beam. [ 37 ]…”

“…This multilayer reflective design was adopted to increase the efficiency and broaden the working wavelength range. [ 36–38 ] Moreover, two opposite phase gradients along the x axis (see axes in Figure a), with phase increment between neighboring nanoantennas, were incorporated into the design of the metasurface to deflect the generated beams at angles for a wavelength of 1550 nm. This off‐axis design avoided the presence of spurious unconverted light in the deflected beam paths.…”

“…For the case of linearly polarized light, which can be expressed as a superposition of RCP and LCP light, two vortex beams with opposite topological charges of + and − are simultaneously generated, giving rise to a vector beam. [37] A SiO 2 layer (220 nm thickness) and a gold ground layer (150 nm thickness) were deposited on a silicon substrate before nanoantenna fabrication. This multilayer reflective design was adopted to increase the efficiency and broaden the working wavelength range.…”

“…[33] In this work, we extend this concept to provide the theoretical description and experimental verification of the rotational Doppler frequency shift arising from the temporal evolution of the high-order PB phase on the TAM Poincaré sphere. To overcome the complexity of typical interferometric schemes [32,34,35] in the evaluation of the PB phase, we use a reflective metasurface [36][37][38] operating at telecom wavelengths, to directly generate a superposition of two vortex beams with high TAM values and opposite signs.…”