Metasurface Polarimetry: Fabrication and Characterization of In-line Stokes Polarimeters Based on Polarization Sensitive Nanoantenna Arrays

TLDR: In this article, an in-line (signal-saving) metasurface polarimeter is proposed based on subwavelength-spaced phased arrays of gold nanorod antennas that provide an intensity modulation of scattered light depending on the polarization of the incident light.

Abstract: The polarization of electromagnetic waves (the direction of transversal vibration of its electric field vector) provides essential information about the emitting sources and scattering objects. Its measurement, i.e., optical polarimetry, has a history of more than 200 years and has found various applications in virtually every branch of science and technology. Fabrication of optical metasurfaces that allow the manipulation of electromagnetic waves with sub-wavelength scale structures has become possible thanks to the rapid development of nanotechnology in the last 50 years. Metasurfaces have the potential of simplifying and miniaturizing existing optical components, including polarimeters. This thesis explores the details of a promising metasurface design for the polarimetric measurement of light. This in-line (signal-saving) metasurface polarimeter is based on subwavelength-spaced phased arrays of gold nanorod antennas that provide an intensity modulation of scattered light depending on the polarization of the incident light to measure the full Stokes vector. An analytical model of the radiation pattern of the metasurface is presented and compared with numerical simulations. Polarimeters operating at telecom wavelengths have been fabricated in compact fiber-coupled packages, comprising an ultra-thin metasurface aligned to four or six photodetectors and characterized with high sampling rates. Non-terminating measurements of the polarization state of light by sampling only a small part of the total light intensity have been performed in in-plane and out-of-plane configurations. The error of the polarimeter has been analyzed and analytical and numerical models for the systematic error are presented. The capacity of the miniatuarization of the metasurface polarimeter has been demonstrated by transferring the metasurface to the facet of a single-mode near-infrared optical fiber. To realize such a fiber-based metasurface polarimeter, a novel template stripping transfer lithography method has been developed. The gold nanopattern is stripped from a silicon wafer and transferred to the fiber facet by means of a UV-curable hybrid polymer. In-line polarimetric measurement has been demonstrated by measuring the intensity of four out-of-plane scattering orders while coupling the non-scattered light back into an optical fiber.