Metasurface higher-order poincaré sphere polarization detection clock

Abstract

Accurately and swiftly characterizing the state of polarization (SoP) of complex structured light is crucial in the realms of classical and quantum optics. Conventional strategies for detecting SoP, which typically involves a sequence of cascaded optical elements, are bulky, complex, and run counter to miniaturization and integration. While metasurface-enabled polarimetry has emerged to overcome these limitations, its functionality predominantly remains confined to identifying SoP within the standard Poincaré sphere framework. The comprehensive detection of SoP on the higher-order Poincaré sphere (HOPS), however, continues to be a huge challenge. Here, we propose a general polarization metrology method capable of fully detecting SoP on any HOPS through a single measurement. The underlying mechanism relies on transforming the optical singularities and Stokes parameters into visualized intensity patterns, facilitating the extraction of all parameters that fully determine a SoP. We actualize this concept through a novel meta-device known as the metasurface photonics polarization clock, which offers an intuitive display of SoP using four distinct pointers. As a proof of concept, we theoretically and experimentally demonstrate fully resolving SoPs on the 0th, 1st, and 2nd HOPSs. Our implementation opens up a new pathway towards real-time polarimetry of arbitrary beams featuring miniaturized size, a simple detection process, and a direct readout mechanism, promising significant advancements in fields reliant on polarization.

Fig. 1. Comparison between the polarization detection processes of the conventional configuration and the proposed MPPC.

a The traditional polarization detection system is schematically depicted, consisting of a series of optical elements such as polarizer, quarter-waveplate, mirrors and CCD. Two sets of experimental setups are needed to detect the Stokes parameters |2ψ, 2χ> and optical singularity |m, n > , respectively. b Schematic of polarization detection with the proposed MPPC. The MPPC is capable of fully detecting a beam on the HOPS via a single measurement and displaying the SoP in a readable manner with four pointers

Fig. 2. Concept of the metasurface photon polarization clock.

a Schematic of the designed meta-device capable of converting an incident light beam with unknown SoP into specific output light fields. As an example, a beam (represented as a golden point) located on the surface of a specific HOPS_1,−1 (1-order) is selected. b The top view of the generated light filed in (a). An incident beam with different SAM and OAM is transformed into specific focusing patterns, with which one can resolve the full SoP of the incident beam. c The schematic of the MPPC, which gives an easy-to-read route for recognizing the incident SoP of the photons, with four pointers showing the four parameters (m, n, 2ψ, 2χ) that fully determined an arbitrary SoP

Fig. 3. Design and SEM images of the MPPC.

a Side view and top view of the meta-atom, which composed of an elliptical TiO₂ nanoblock on the SiO₂ substrate. b Calculated PCR as a function of nanoblock’s in-plane dimensions at the working wavelength of 633 nm. c Simulated phase shifts as a function of nanoblock’s in-plane dimensions under x-linearly polarized incident light. The black dots in (b) and (c) denote the selected four fundamental nanoblocks, which simultaneously owns a phase gradient of π/4 and a relatively high PCR. d The phase profile components of the MPPC. The phase profiles of the RCP and LCP components are a sum of an angular lens, a spiral phase plate and a lens, respectively. e Overall SEM image of the meta-device. Scale bar: 30μm. f, g Top view and side view SEM images of part of the sample that marked with the green frame in (e). Scale bar: 1μm

Fig. 4. Resolving SoP of beams on the HOPS_0,0 by using the MPPC.

a, b Simulated and measured intensity (|E_x|²) profiles of the MPPC for incident light with four SoPs from left to right: |0, 0, 0, π/2>, |0, 0, π/2, π/2>, |0, 0, 0, π>, and |0, 0, 0, π/6>. c. The normalized intensity distributions along the turquoise dashed ring shown in (a) and (b). The turquoise and rose red solid lines represent the simulated and measured results, respectively. d The normalized intensity distributions along the turquoise dashed ring shown in the enlarged insets of (a) and (b). The turquoise and rose red solid lines represent the simulated and measured results, respectively. The black triangle marks in (c) and (d) represent the azimuth angle of the intensity peaks. e, f Numerically and experimentally retrieved SoPs by the MPPC, where the SoPs can be directly readout by four pointers

Fig. 5. Resolving SoP of beams on the HOPS_1,−1 and HOPS_2,−2.

a Measured intensity (|E_x|²) profiles of the MPPC for incident light with six SoPs from left to right: |1, −1, 0, π/2>, |1, −1, π, π/2>, |1, −1, 5π/3, π/2>, |1, −1, 0, 0>, |1, −1, 0, π>, and |1, −1, π, π/6>. b Experimentally retrieved SoPs by the MPPC, where the SoPs can be directly readout by four pointers. c Original (red points) and reconstructed (green asterisks) SoPs represented on the HOPS_1,−1. d Measured intensity (|E_x|²) profiles of the PPC for incident light with six SoPs from left to right: |2, −2, 0, π/2>, |2, −2, π, π/2>, |2, −2, 3π/2, π/2>, |2, −2, 0, 0>, |2, −2, 0, π>, and |2, −2, 0, π/6>. e Experimentally retrieved SoPs by the MPPC, where the SoPs can be directly readout by four pointers. f Original (red points) and reconstructed (green asterisks) SoPs represented on the HOPS_2,−2