Nonlinear terahertz metamaterials with active electrical control

Abstract

We present a study of an electrically modulated nonlinear metamaterial consisting of an array of split-ring resonators fabricated on n-type gallium arsenide. The resonant metamaterial nonlinearity appears as an intensity-dependent transmission minimum at terahertz frequencies and arises from the interaction between local electric fields in the split-ring resonator (SRR) capacitive gaps and charge carriers in the n-type substrate. We investigate the active tuning range of the metamaterial device as the incident terahertz field intensity is increased and conversely the effect of an applied DC bias on the terahertz field-induced nonlinear modulation of the metamaterial response. Applying a DC bias to the metamaterial sample alters the nonlinear response and reduces the net nonlinear modulation. Similarly, increasing the incident terahertz field intensity decreases the net modulation induced by an applied DC bias. We interpret these results in terms of DC and terahertzfield-assisted carrier acceleration, scattering, and multiplication processes, highlighting the unique nature of this DC-field modulated terahertz nonlinearity. Published by AIP Publishing.

Generation of spatiotemporally tailored terahertz wavepackets by nonlinear metasurfaces

“…Engineered metasurfaces and metamaterials 15 were demonstrated to be useful for development of various new types of optical THz elements. Engineered absorption 16 , polarization conversion 17 , active phase modulation 18 , and even nonlinear effects 19,20 were observed in THz metamaterials. In addition, optical metasurfaces were proven to enhance the THz emission from photoconductive antennas 21 .…”

Terahertz driven amplification of coherent optical phonons in GaAs coupled to metallic dog-bone resonators

“…This problem is circumvented when generating a terahertz-driven transient electron distribution displaying an inversion situation for optical phonons. Here, we apply terahertz fields enhanced by a metallic dog-bone resonator [2] to generate such a carrier distribution and amplify coherent optical phonons in GaAs within a short time period of 2 ps. The time evolution of the coupled phonon-carrier system is mapped with the help of two-color two-dimensional (2D) THz spectroscopy [3].…”

A Review of THz Modulators with Dynamic Tunable Metasurfaces

“…Based on the similar principle of the Schottky diode, the same team [9] reported a hybrid metamaterial phase modulator, obtaining a linear shift of 0.56 rad. Afterwards, researchers realized that the efficient combination of semiconductors and metasurfaces presents a reliable way to regulate terahertz waves [35,36,37,38,39]. D.M.…”

“…In 2017, the same team designed an electrically modulated nonlinear metamaterial made of an SRR array grown on n-type gallium arsenide. The interaction between the electric field in the SRR and the carrier in the gallium arsenide cause a nonlinearity, which could be modulated by the voltage applied to the device (Figure 4c) [39]. In addition, a metamaterial modulator with two independent channels can actively modulate the terahertz waves of the corresponding channel by independently controlling the depletion zone of the two types of the Schottky structure under a bias voltage.…”