Performance characteristics of 4-port in-plane and out-of-plane in-line metasurface polarimeters

Abstract

In-line polarimeters perform nonterminating measurements of the polarization state of light by sampling only a small part of the total light intensity. In-line polarimeters are used in applications such as polarization state generators and in optical communications. Current polarimeters use multiple optical components in sequence for polarization analysis and therefore often become bulky and expensive. Here, we experimentally demonstrate the operation of compact fiber-coupled polarimeters with high sampling rates, operating at telecom wavelengths, each polarimeter comprising a single ultra-thin metasurface aligned to four photodetectors. We compare two configurations of such metasurface polarimeters, with in-plane and out-of-plane detection, respectively. The metasurface polarimeters reported here show excellent agreement with commercial polarimeters and cover a bandwidth of at least 100 nm.

Metasurface Polarimeter on Optical Fiber Facet by Nano-Transfer to UV-Curable Hybrid Polymer

“…The distance between the two columns of perpendicularly oriented antennas is λ(1+1/4) and the column-pairs are spaced 2λ, where λ is the design wavelength in the polymer material, corresponding also roughly to the resonance wavelength of the individual antennas. When near-infrared light (C-band wavelengths) is normally incident on the metasurface, a fraction of the intensity is scattered in polarization-dependent in-plane and out-of-plane meta-grating orders; each order serving as a polarization analyzer [25]. The in-plane grating orders stay in the plane of the metasurface, whereas light in the out-of-plane orders is scattered at an angle close to 45° from the metasurface plane after refraction at the polymer/air interface.…”

“…The images were recorded with arbitrary brightness by placing the structured fiber directly in front of the infrared camera. The signal from the diodes was amplified and sampled using a microcontroller that collected 300-sample sets at a rate of 1 kHz [25]. The transmitted light was coupled back into a second fiber, which was attached to another xyz stage and positioned approximately 100 µm from the metasurface, obtaining a coupling efficiency of about 50 % (-3 dB) where about 3 % can be related to reflection losses.…”

“…28 − 29 % of the total incoming power is lost in the metasurface polarimeters. The scattered and absorbed power in the metasurface is approximately equal [28] and the scattered power is distributed to a total of 16 scattering orders [25]. The power arriving at each detector is 0.4 − 0.5 % of the total incoming power in case of the flood exposure design and 0.1 − 0.2 % in case of the fiber exposure design.…”

“…The antenna arrays of the wafer-based metasurface polarimeter are embedded in layers of benzocyclobutene (BCB) polymer on top of a fused silica wafer. More fabrication details can be found in [25]. Polarization measurements (red circles) of a wafer-based polarimeter are shown in Fig.…”

Polarization state generation and measurement with a single metasurface

“…We characterize such a polarimeter and compare its performance to a commercial rotating-waveplate instrument. In contrast to previous work by us [20,21] on terminating polarimeters and by others [22][23][24][25][26][27] on a variety of metasurface/metamaterial-based schemes, the present work allows for the generation and analysis of polarization on channels whose polarizations may themselves be arbitrarily specified, demonstrates full-Stokes vector determination (including partially polarized light), and provides a quantitative error analysis. As such, it is of consequence for any application requiring low-cost, easily integrated polarimetry or polarization imaging and is a testament to the flexibility of metasurfaces in the realm of polarization optics.…”