Schematic of the passive near-field probe. A linearly polarized free-space propagating field can be efficiently converted in a radially polarized wire mode, and vice versa; thanks to a Teflon discontinuous phase element.
Transverse electric field as measured at the passive probe end located at the position . [(a) and (b)] Transverse electric field measured in the -plane normal to the wire at ; the gray arrow indicates the polarization measured by the analyzer. (c) Vertical component of the electric field (located in the plane of the figure) measured in the -plane.
Probe-to-probe coupling experiment. (a) Experimental arrangement. The left probe is illuminated by the 0.1 THz source using parabolic mirrors. The output of the right probe is feed in a rectangular horn coupled to a WR10 waveguide that includes the Schottky diode detector. For convenience in the scheme, the two Teflon DPEs are represented with the same orientation although in practice they were -cross-oriented to reduce the direct transmission. (b) Coupled power as measured in the -plane normal to the wire at . (c) -direction FWHM of the transmitted power as measured for various distances between the two probes.
Calculated electric field magnitudes in a plane orthogonal to the wire and at the close distance . (a) Profiles of (solid line) and (dashed line). (b) Image of .
Probe-to-probe transmitted power at the prescribed (, ) coordinate and as a function of the vertical displacement . Squares are measurements and lines are calculations from Eq. (1) using as input the data of the FDTD calculations. Dash-dotted line: radial component alone. Dotted line: longitudinal component alone. Solid line: total field. Dashed line: Gaussian profile of the background noise contribution.
Probe-to-probe transmitted power as a function of the -direction. The two identical probes use 4 cm long sharp needles. ◻, measured coupling between the two needles placed in front as a function of the distance between them. , same measurement with one needle removed. The inset gives the measured difference between previous data (◇) and gives a close view limited to . Also plotted is an exponential fit (solid line).
Calculated intensities of the electric field vector components as transmitted through the subwavelength square holes whose imprints are drawn in white for convenience. (a) , (b) , and (c) .
Near-field imaging of subwavelength square holes in a thin metal film. (a) Experimental arrangement. (b) Near-field intensity acquisition.
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