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We present an analytical model describing the transition to a strong coupling regime for an ensemble of emitters resonantly coupled to a localized surface plasmon in a metal–dielectric structure. The response of a hybrid system to an external field is determined by two distinct mechanisms involving collective states of emitters interacting with the plasmon mode. The first mechanism is the near-field coupling between the bright collective state and the plasmon mode, which underpins the energy exchange between the system components and gives rise to exciton-induced transparency minimum in scattering spectra in the weak coupling regime and to emergence of polaritonic bands as the system transitions to the strong coupling regime. The second mechanism is the Fano interference between the plasmon dipole moment and the plasmon-induced dipole moment of the bright collective state as the hybrid system interacts with the radiation field. The latter mechanism is greatly facilitated by plasmon-induced coherence in a system with the characteristic size below the diffraction limit as the individual emitters comprising the collective state are driven by the same alternating plasmon near field and, therefore, all oscillate in phase. This cooperative effect leads to scaling of the Fano asymmetry parameter and of the Fano function amplitude with the ensemble size, and therefore, it strongly affects the shape of scattering spectra for large ensembles. Specifically, with increasing emitter numbers, the Fano interference leads to a spectral weight shift toward the lower energy polaritonic band.
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Experimental confirmation of phase profile of Hermite–Gauss beams
Phase distribution of Hermite–Gauss (HG) beams generated by a gas laser is investigated experimentally by studying their interference with a plane wave and diffraction by a single slit by selecting pairs of bright lobes with different phases. Experimentally recorded interference and diffraction profiles support HG mode phase profiles expounded on in this paper. We find that the phase difference between one bright lobe and another is not simply zero orπbut increases (or decreases) uniformly in steps ofπas the number of zeros between them increases, in agreement with analytic function theory. An immediate application of this phase profile is that an HG mode can serve as a phase ruler with bright lobes as markers in steps ofπ.
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- PAR ID:
- 10546798
- Publisher / Repository:
- Optical Society of America
- Date Published:
- Journal Name:
- Journal of the Optical Society of America A
- Volume:
- 41
- Issue:
- 11
- ISSN:
- 1084-7529; JOAOD6
- Format(s):
- Medium: X Size: Article No. 2023
- Size(s):
- Article No. 2023
- Sponsoring Org:
- National Science Foundation
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