Multichannel probes for polarization-resolved scanning near-field optical microscopy

Abstract

We propose and validate a concept of multichannel near-field fiber probe for the collection and discrimination of optical fields of orthogonal polarizations (linear, elliptic, and circular). The system is achieved by connecting to scanning near-field optical microscope fiber tips an optical stage made up of commercial polarizers, fiber couplers, and polarization controllers. Using radially polarized Bessel beams as test objects, we demonstrate the ability of a three-channel fiber tip to simultaneously and independently probe the transverse vector components of the electric field (parallel to the sample surface) and the overall transverse intensity. The polarization ratio of the near-field collection system exceeds 1:1500. The system can be implemented in collection-mode or reflection-mode near-field microscope configurations, with various kinds of probe and light source (of high or low coherence lengths) for a deeper insight of light polarization effects and vector fields at a subwavelength scale.

Polarization-Resolved Near-Field Mapping of Plasmonic Aperture Emission by a Dual-SNOM System

“…Different techniques have been implemented in order to control the orientation of an illumination tip’s electromagnetic near-field, either by modifying the aperture − or by influencing the polarization state of light that reaches the aperture. The latter can be achieved by either tuning the polarization state inside the fiber with free-space or fiber polarizers, or by using polarization-maintaining fibers. , In some cases, the orientation of the transverse fields is preserved over the transmission through the fiber and the tip; ,, other tip designs act as linear polarizers. − ,, …”

“…The latter can be achieved by either tuning the polarization state inside the fiber 32 with free-space or fiber polarizers, or by using polarization-maintaining fibers. 33,34 In some cases, the orientation of the transverse fields is preserved over the transmission through the fiber and the tip; 27,33,35 other tip designs act as linear polarizers. [29][30][31]36,37 While Dual-SNOM measurements require an understanding of the polarization characteristics of the excitation as well as the detection process, they can also be used as a tool to assess and confirm these characteristics.…”