Optical fiber meta-tips: Supplementary information


Supplementary Figure S4 |



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Supplementary Figure S4 |Schematic of the experimental setup for far-field characterization without polarization control. For the polarization measurements, a fiber polarization controller is connected at the output of the tunable laser, and a linear polarizer is mounted on a continuous rotation mount positioned right before the vidicon camera.

Experimental characterization

Supplementary Figure S4schematically illustrates the far-field experimental setup.To facilitate direct comparison with the numerical predictions (cf. Figure 4), the acquired field-intensity maps are suitably normalized (with respect to the maximum values), rotated and registered so as to have the peak corresponding to the ordinary beam at coordinates . The transmission angles are estimated via a differential scheme (see Supplementary Figure S5), by measuring the separation between the two main peaks at two different distances from the receiving window of the vidicon camera, whose difference is accurately controlled via the micro-positioning system.We therefore obtain the estimate

33\* MERGEFORMAT (S)

By taking into account the resolution of the micrometer positioning system as well as the pixel size of the acquired images, we estimate a uncertainty.



Supplementary Figure S5 |Transmission-angle measurement.Illustration (not in scale) of the differential measurement scheme [see Equation 3].



For the polarization measurements (see Figure 5 and Supplementary Movie 1), the position of the MT sample on the plastic holder is judiciously adjusted so as to align the phase-gradient direction (x-axis in the assumed reference system; see Figure 1) parallel to the vidicon camera horizontal axis. By suitably acting on the fiber polarization controller and the linear polarizer, the incident polarization on the MT is aligned with the y-axis, in such a way the ordinary and anomalous beams are fiducially polarized along the y- and x- directions, respectively. The measurements in Figure 5 and Supplementary Movie 1 are performed by suitably rotating the polarizer so as to select specific linear-polarization states of the transmitted field.

Supplementary Figure S6 |Schematic of the experimental setup for surface-sensitivity characterization.

Supplementary Figure S6 shows a schematic of the surface-sensitivity experimental setup. To minimize the influence of the light-source spectral features, as well as of the losses introduced by the optical chain, the acquired spectrum is normalized by that of a reference mirror fabricated by depositing a 160 nm gold layer on the facet of a standard single-mode fiber. To filter out random noise, the normalized spectrum is finally smoothed via the filtfilt function (zero-phase digital filtering) available in Matlab (www.mathworks.com).




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