Reversible modulation and ultrafast dynamics of terahertz resonances in strongly photoexcited metamaterials

Abstract

We demonstrate an ultrafast reversible modulation of resonant terahertz (THz) response in strongly photoexcited metamaterials. The transient spectral-temporal response of the dipole transition ∼1.6 THz exhibits a distinct non-monotonic variation as a function of pump fluence. The transition energy shift, strength, spectral width, and density-dependent ultrafast relaxation manifest a remarkable re-emergence of the transmission dip after initial quenching. Our simulations, incorporating the first-order diffraction from the photoinduced transient grating, reproduce the salient features, providing a new avenue for designing nonlinear and frequency-agile THz modulators.

Active Photoswitching of Sharp Fano Resonances in THz Metadevices

“…[15,16] These studies were focused on optimizing the Fano resonance strength by altering the geometry of the MM structures in a passive way. On the other hand, by integrating the MM with the photoactive materials [25][26][27][28][29][30] such as silicon has shown the active modulation of resonance properties in the MM system in a desirable fashion. [17][18][19][20][21] For example, reconfigurable metamaterials [22][23][24] are being used to actively tune the near field coupling by applied voltage or by thermal actuation.…”

Broadband terahertz generation from metamaterials

“…However, the relatively small nonlinear susceptibilities of inorganic emitters limit the THz emission intensity. Meanwhile, nonlinear metamaterials have been actively pursued [11][12][13][14][15][16][17][18][19] , and the recent development of metamaterials composed of split-ring resonators (SRRs) has enabled researchers to tailor resonant optical nonlinearities from the THz to the infrared and visible regions 20,21 . In this regard, investigating metamaterials with few tens of nanometres thickness exhibiting artificial optical magnetism-that is, sustaining circulating ring currents at optical frequencies-can meet the urgent demand for new nonlinear materials for optical rectification free from both quasi-phase-matching limitation and spurious THz phonon absorption.…”

Programmable Metasurfaces: State of the Art and Prospects

“…Several implementations with split-ring-resonator-based metasurfaces operating in the THz have been proposed. In [31], [32], the semiconductor (GaAs) is included as the substrate material. Alternatively, the semiconductor (Si) can be incorporated as a section in the resonant structure [11], [33].…”