  THz metamaterials present unique opportunities for next generation
technologies and applications, as they can fill the ``THz gap'' originating
from the weak response of natural materials in this regime, providing a variety
of novel or advanced electromagnetic wave control components and systems. Here,
we propose a novel metamaterial design, made of three-dimensional, metallic,
"cactus like" meta-atoms, showing electromagnetically induced transparency
(EIT) and enhanced refractive index sensing performance at low THz frequencies.
Following a detailed theoretical analysis, the structure is realized
experimentally using multi-photon polymerization and electroless silver
plating. The experimental characterization results obtained through THz time
domain spectroscopy validate the corresponding numerical data, verifying the
high potential of the proposed structure in slow light and sensing
applications.
