We report on terahertz focusing through rectangular slit apertures on thinmetal film by using terahertz time domain spectroscopy both in the far- andin the near-field. Our experiments show that far-field perfect transmissionis maintained in the rectangular slit array even as the aperture coveragedecreases. Near-field imaging supports the field enhancement in the singlerectangular aperture indeed occurring at a frequency equal to thefundamental shape resonance frequency.

Keywords: Terahertz, Optical spectroscopy, Plasmonic metamaterials