  The gain-assisted plasmonic analogue of electromagnetically induced
transparency (EIT) in a metallic metamaterial is investigated for the purpose
to enhance the sensing performance of the EIT-like plasmonic structure. The
structure is composed of three bars in one unit, two of which are parallel to
each other (dark quadrupolar element) but perpendicular to the third bar
(bright dipolar element), The results show that, in addition to the high
sensitivity to the refractive-index fluctuation of the surrounding medium, the
figure of merit for such active EIT-like metamaterials can be greatly enhanced,
which is attributed to the amplified narrow transparency peak.
