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Abstract Polarization, as a fundamental property of light, plays a key role in many phenomena of near‐field coupling, namely the coupling of source's evanescent waves into some guided modes. As a typical example of the polarization‐locked phenomenon in the near‐field coupling, the Janus dipole has the orientation of its near‐field coupling face intrinsically determined by the polarization state of linearly‐polarized surface waves, specifically whether they are transverse‐magnetic (TM) or transverse‐electric (TE) surface waves. Here, a mechanism to achieve the directional near‐field coupling of Janus dipoles beyond polarization locking by leveraging hybrid TM‐TE surface waves is presented. These hybrid surface waves, as eigenmodes with both TM and TE wave components, can be supported by optical interfaces between different filling materials inside a parallel‐plate waveguide. Under the excitation of hybrid surface waves, it is found that the coupling and non‐coupling face of a Janus dipole may be switched, if the Janus dipole itself rotates in a plane parallel to the designed optical interface between different filling materials, without resorting to the change of surface‐wave polarization. The underlying mechanism is due to the capability of hybrid surface waves to extract both the source's TM and TE evanescent waves, which offers an alternative paradigm to regulate the interference in the near‐field coupling.
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Excitation of surface plasmon polaritons by diffraction-free and vector beams
Surface plasmon polaritons (SPPs) are traditionally excited by plane waves within the Rayleigh range of a focused transverse-magnetic (TM) Gaussian beam. Here we investigate and confirm the coupling between SPPs and two-dimensional Gaussian and Bessel–Gauss wave packets, as well as one-dimensional light sheets and space-time wave packets. We encode the incoming wavefronts with spatially varying states of polarization; then we couple the respective TM components of radial and azimuthal vector beam profiles to confirm polarization-correlation and spatial-mode selectivity. Our results do not require material optimization or multi-dimensional confinement via periodically corrugated metal surfaces to achieve coupling at a greater extent, hereby outlining a pivotal, yet commonly overlooked, path towards the development of long-range biosensors and all-optical integrated plasmonic circuits.
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- Award ID(s):
- 2027321
- PAR ID:
- 10370205
- Publisher / Repository:
- Optical Society of America
- Date Published:
- Journal Name:
- Applied Optics
- Volume:
- 61
- Issue:
- 25
- ISSN:
- 1559-128X; APOPAI
- Format(s):
- Medium: X Size: Article No. 7469
- Size(s):
- Article No. 7469
- Sponsoring Org:
- National Science Foundation
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