  We report an experimental observation of three distinct resonances in split
ring resonators (SRRs) for both vertical and horizontal electric field
polarizations at normal incidence by use of terahertz time domain spectroscopy.
Breaking the symmetry in SRRs by gradually displacing the capacitive gap from
the center towards the corner of the ring allows for an 85% modulation of the
fundamental inductive-capacitive resonance. Increasing asymmetry leads to the
evolution of an otherwise inaccessible high quality factor electric quadrupole
resonance that can be exploited for bio-sensing applications in the terahertz
region.
