Ultra-narrow resonances and near-field energy density enhancement in planar cross-linked metamaterials

► The positive/negative metamaterials with quartz substrate built by cross-linked asymmetrically split rings (ASR) or apertures are theoretically investigated based on a full three-dimensional Maxwell finite element method, which will be good candidates for developing low-loss freestanding metamaterials. ► The asymmetry provides an easy and practical way to tune the electromagnetic response of metamaterails. The positive metamaterial on quartz glass shows the quality factor of up to 1000. ► The near-field energy density enhancement 0.1 mm above the ASR metamaterial on glass substrate reaches the ultra-high value of 150000, 500 times stronger than that of fundamental dipole resonance. The energy density enhancement factor falls by a factor of 10 only increasing the distance above the meta-surface to 0.5mm.