Plasmon-induced transparency effect in hybrid terahertz metamaterials with active control and multi-dark modes

Abstract

In this work, we numerically demonstrate a photo-excited plasmon-induced transparency (PIT) effect in hybrid terahertz (THz) metamaterials. The proposed metamaterials are regular arrays of hybrid unit cells composed of a metallic cut wire and four metallic split-ring resonators (SRRs) whose gaps are filled with photosensitive semiconductor Gallium arsenide (GaAs) patches. We simulate the PIT effect controlled by external infrared light intensity to change the conductivity of GaAs. In the absence of photo excitation, the conductivity of GaAs is 0, thus the SRR gaps are disconnected, and the PIT effect is not observed since the dark resonator (supported by the hybrid SRRs) cannot be stimulated. When the conductivity of GaAs is increased via photo excitation, the conductivity of GaAs can increase rapidly from 0 to 1 × 106 s/m and GaAs can connect the metal aluminum SRR gaps, and the dark resonator is excited through coupling with the bright resonator (supported by the cut wire), which leads to the PIT effect. Therefore, the PIT effect can be dynamically tuned between the on and off states by controlling the intensity of the external infrared light. We also discuss couplings between one bright mode (CW) and several dark modes (SRRs) with different sizes. The interference analytically described by the coupled Lorentz oscillator model elucidates the coupling mechanism between one bright mode and two dark modes.The phenomenon can be considered the result of linear superposition of the coupling between the bright mode and each dark mode. The proposed metamaterials are promising for application in the fields of THz communications, optical storage, optical display, and imaging.

Integrated system of traditional THz time-domain spectroscopy and asynchronous optical sampling

“…Terahertz (THz) wave is located between microwave and infrared, and the frequency ranges from 0.1 THz to 10 THz. [1] The data rates of this band can be expanded to terabits per second. [2] The discovery of laser-induced ultrafast demagnetization provides a perfect platform to manipulate spins on a sub-picosecond timescale and opens up a promising route to developing future information technology at THz speed.…”

Improved Huygens’ Principle for Metamaterial

“…Thus, the original Huygens' principle cannot deal with metamaterial with coupling [5]. Normally, calculating transmission spectra with coupling between metamaterial structures exploits coupled mode theory (CMT) [8][9][10][11], which explains the coupling of many metamaterial phenomena, such as electromagnetic-induced transparency (EIT) [12][13][14], bound states in the continuum (BIC) [15][16][17] and parity-time (PT) symmetry [18][19][20][21][22]. However, the shortcoming of CMT is that it is very complex to calculate transmission spectra for complex and large-sized metamaterial arrays and it is also necessary to introduce some fitting numbers to obtain the transmission spectra.…”