Role of avoided crossing and weak value amplification on enhanced Faraday effect in magnetoplasmonic systems

Abstract

Enhancement of magneto-optical effects in hybrid magneto-plasmonic systems has attracted considerable recent attention because of their potential for building non-reciprocal nanophotonic devices. Quantitative understanding of the fundamental origin and contributing mechanisms for the enhancement is crucial for optimizing applications. Here, we unravel different physical origins of the giant enhancement of Faraday rotation and ellipticity in a hybrid magneto-plasmonic system, namely, waveguided magneto-plasmonic crystal for excitation with transverse electric (TE) and transverse magnetic (TM) polarized light. With TE polarization excitation, where the surface plasmons are not directly excited, the natural weak value amplification of Faraday effects appearing due to the spectral domain interference of Fano resonance is the dominant cause of the enhancement. For TM polarization excitation, on the other hand, waveguide-plasmon strong coupling and its universal manifestation of avoided crossing plays an important role, leading to maximum enhancement of the magneto-optical effects in the avoided crossing regime.

Simultaneous observation of forward and inverse spin-Hall effects in a hybridised spin-locking plasmonic crystal

“…The optimized dimensions of the Au grating are:-width approx 90 nm, height approx 20 nm, center to center distance 550 nm. With incident transverse magnetic (TM-y) polarized light (electric field perpendicular to the grating lines), interference between the discrete TM quasiguided modes and the broad surface plasmon mode lead to Fano resonance with asymmetric spectral line shape [12]. With TE-x polarization excitation (electric field parallel to the grating lines), Fano resonance arises due to the interference of the TE quasiguided modes with the photon continuum [12].…”

“…With incident transverse magnetic (TM-y) polarized light (electric field perpendicular to the grating lines), interference between the discrete TM quasiguided modes and the broad surface plasmon mode lead to Fano resonance with asymmetric spectral line shape [12]. With TE-x polarization excitation (electric field parallel to the grating lines), Fano resonance arises due to the interference of the TE quasiguided modes with the photon continuum [12]. The geometrical parameters of the WPCs are tailored (based on finite element method simulation [12]to achieve strong spectral overlap between the narrow TM and the TE quasiguided modes and the broad surface plasmon resonance.…”

“…With TE-x polarization excitation (electric field parallel to the grating lines), Fano resonance arises due to the interference of the TE quasiguided modes with the photon continuum [12]. The geometrical parameters of the WPCs are tailored (based on finite element method simulation [12]to achieve strong spectral overlap between the narrow TM and the TE quasiguided modes and the broad surface plasmon resonance. Then, for either with TM or TE polarization excitation, the WPC exhibits Fano resonance (within λ=460 -580 nm) having strong amplitude anisotropy (linear diattenuation -𝑑 𝑤𝑝𝑐 ) and phase anisotropy (linear retardance -δwpc) effects [12].…”

“…The geometrical parameters of the WPCs are tailored (based on finite element method simulation [12]to achieve strong spectral overlap between the narrow TM and the TE quasiguided modes and the broad surface plasmon resonance. Then, for either with TM or TE polarization excitation, the WPC exhibits Fano resonance (within λ=460 -580 nm) having strong amplitude anisotropy (linear diattenuation -𝑑 𝑤𝑝𝑐 ) and phase anisotropy (linear retardance -δwpc) effects [12]. The leakage radiation from the quasiguided modes is collected in our darkfield microscope to record both the polarization-resolved Fourier (momentum) domain Mueller matrix images and the spectral polarization response of the WPCs.…”

Acoustic analog to multiple avoided-crossings in two coupled acoustic cavities

“…It is important for quantum dynamics [2,3]. It has helped in manipulating quantum state of an atom [4], in controlling entanglement between magnetic molecules [5] and in enhancing the Faraday effect [6].…”