Terahertz resonance frequency shifting in metamaterial metal line array fabricated on photoconductive antennas
Abstract
Frequency shifting of the THz emission spectra of photoconductive antenna devices was demonstrated by utilizing a metamaterial consisting of gold metal line arrays. Two devices with array periodicities of ~400 μm and ~100 μm were investigated, with calculated first order resonance frequencies of ~0.2 THz and ~0.8 THz, respectively. The THz emission spectra of both devices shifted relative to the reference photoconductive antenna, toward the resonance frequencies. For the device having a 100 μm period, both a spectral shift and increase in THz power at lower frequencies was observed, which may be attributed to spoof plasmonic interactions originating from metal lines having separation distances greater than 100 μm. The results show the feasibility of tailoring the periodicity of the metamaterial structures to adjust the operating frequencies of THz devices.