Utilizing terahertz time domain spectroscopy system, we have characterized the electromagnetic
response of a planar array of split ring resonators (SRRs) fabricated upon a high resistivity GaAs
substrate. We discuss the phenomena of resonant transmission and absorption experimentally, and
analyze the factors that affect the frequency of the resonant transmission peak. Free charge in metal
rings occurs directional moving with effects of electric and magnetic fields when terahertz wave is
incident in split ring (SR). It makes transmission and absorption peaks at certain frequencies by electric
and magnetic responses between metal rings. There is another kind of absorption which is made by its
structure at natural frequency of SR. We demonstrate, SRR structure has anisotropic property. The
directions of split will decide transmission mode of terahertz in samples. Different modes of dipole
oscillating are made by changing electric wave vector, and its absorption is also affected. However,
natural frequency of SRR is decided by lattice size, independent of transmission mode. Magnetic
response occurs when magnetic wave vector has component which is normal to sample surface. It
makes phenomenon of absorption more apparently. In addition, decreasing component of which is
parallel to sample surface can make transmission peak move to low frequency. Infections to resonance
properties of SRR by terahertz electric and magnetic wave vectors are discussed in this letter. It can be
a reference for researching terahertz devices.
Recently, more and more groups are concentrating on learning surface plasma on metal split with sub-wavelength of
terahertz. There is a new material which is made of two materials named metamaterial. It is combined with
semiconductor and metal materials. Metal parts are made with subwavelength microstructure. Abnormal phenomenon
occurred when it is excited by an intense light, showing an enhancement transmission of terahertz wave. In this paper,
we design a planar structure composed of gallium arsenide (substrate) and copper (metal). Copper array is plating on a
GaAs wafer on order of micron with photoetching technology. The thickness of GaAs and copper layer are 650 and 0.5
micros individually. THz incidence has an enhanced transmission like surface plasmonic resonance with terahertz
time-domain system when another exciting lighted on, which made current carriers in photoconductor. This resonance
arises from an inductor-capacitor circuit resonance. Comparison is performed between results with and without
excitation. The angle of sample plane with terahertz polarization and incidence can affect this electromagnetic response
in some degree. Its transmittance with back-incidence is much stronger than that with front-incidence at certain
frequencies. This kind of artificial structure has potential abilities in terahertz devices in the future. It is helpful to
develop terahertz filter, polarizing film, beam reflector, phase retarder and so on.
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