  Enhancement of magneto-optical effects in hybrid magneto-plasmonic systems
has attracted considerable recent attention owing to their potential for
building non-reciprocal nanophotonic devices. Quantitative understanding on the
fundamental origin and contributing mechanisms for the enhancement is extremely
crucial for optimizing applications. Here, we unravel the distinctly different
physical origin 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 intriguing role, leading to maximum enhancement of
the magneto-optical effects in the avoided crossing regime.
