  Weak measurement enables faithful amplification and high precision
measurement of small physical parameters and is under intensive investigation
as an effective tool in metrology and for addressing foundational questions in
quantum mechanics. Most of the experimental reports on weak measurements till
date have employed external symmetric Gaussian pointers. Here, we demonstrate
its universal nature in a system involving asymmetric spectral response of Fano
resonance as the pointer arising naturally in precisely designed metamaterials,
namely, waveguided plasmonic crystals. The weak coupling arises due to a tiny
shift in the asymmetric spectral response between two orthogonal linear
polarizations. By choosing the pre- and post-selected polarization states to be
nearly mutually orthogonal, we observe both real and imaginary weak value
amplifications manifested as spectacular shift of the peak frequency of Fano
resonance and narrowing (or broadening) of the resonance line width,
respectively. Weak value amplification using asymmetric Fano spectral response
broadens the domain of applicability of weak measurements using natural
spectral line shapes as pointer in wide range of physical systems.
