Optical Materials Express, Vol. 1, Issue 2, pp. 151-157 (2011) doi:10.1364/OME.1.000151
Large-area split ring resonators (SRRs) array is fabricated by laser micro-lens array (MLA) lithography on flexible Polyethylene Naphthalate (PEN) substrates. Multi-layer metamaterials are formed by stacking and bonding several layers of the laser fabricated metamaterials together. The resonance of the multi-layer metamaterials is enhanced significantly as compared to the single-layer metamaterials. The roll-off value of the half-wavelength resonant dip, which reflects the strength of resonance, increases significantly from 4.9 to 11.2 as the layer number increases from 1 to 5. A logarithm relationship between the amplitude of the resonant dip and the layer number is also studied, which indicates a flexible method to tune the strength of resonance by changing the layer number. The multi-layer metamaterials with the enhanced resonance can be used to make narrow band terahertz filters.
“The samples are characterized by a Terahertz Time Domain Spectroscopy (THz-TDS,
TPS3000, Teraview Inc.) in transmission mode at a normal incidence. The electric field of the
incident terahertz wave is aligned parallel to the gap-bearing side of the SRRs as illustrated in
Fig. 1 (B). All the transmission spectra of the samples with different layer numbers are
normalized against the reference transmission spectrum of Nitrogen gas environment ”