Anomalous Wavelength Scaling of Tightly Coupled Terahertz Metasurfaces.

We theoretically and experimentally demonstrate the drastic changes in the wavelength scaling of tightly coupled metasurfaces caused by deep subwavelength variations in the distance between the unit resonators but no change in the length scale of the units themselves. This coupling-dependent wavelength scaling is elucidated by our model metasurfaces of ring resonators arranged with deep subwavelength lattice spacing g, and we show that narrower g results in rapider changes in wavelength scaling. Also, by using terahertz time-domain spectroscopy, we experimentally observed a significant shift of the spectral response arising from very small variations in lattice spacing, confirming our theoretical predictions.