  The toroidal dipole excitation is an important field for metamaterial
research because of their low-loss attribute. In this study, we demonstrate
numerically and experimentally, a unique polarization independent terahertz
metamaterial that modulates a broad resonance into a sharp mode by coupling the
inherent toroidal dipole excitation to the lattice mode of the metasurface. The
advantage of polarization independence in the metasurface enables the
excitation of lattice-coupled toroidal mode for both the transverse electric
and transverse magnetic modes of the incident terahertz radiation. The
interaction of the two dark low-loss modes results in the significant
enhancement of the quality factor of the metasurface at the point of resonance
matching. Such a polarization independent lattice-matched toroidal
excitation-based device has the potential to impact the development of low loss
terahertz component for ultrasensitive sensors, low loss equipment, and slow
light devices for enhanced light matter interaction.
