Ultrafast strong-field terahertz nonlinear nanometasurfaces

Area of Science:

• * Physics and Applied Sciences
• * Materials Science and Nanotechnology
• * Nonlinear Optics and Electromagnetics

Background:

• * Strong-field terahertz (THz) interactions are crucial for studying nonequilibrium phenomena in the nonperturbative regime.
• * Limited availability of high-field, high-repetition-rate, high-quality THz sources impedes research progress.
• * Investigating THz-matter interactions at the nanoscale requires advanced techniques for field enhancement.

Purpose of the Study:

• * To investigate the nonlinear modulation dynamics of a THz-nano metasurface under strong-field THz excitation.
• * To explore the potential of confined THz fields for ultrafast time-resolved nanoscale THz-matter interactions.
• * To develop new strategies for THz nonlinear modulation devices and THz science in nonextreme laboratory settings.

Main Methods:

• * Utilized a time-resolved strong-field THz-pump THz-probe (TPTP) spectroscopy technique.
• * Employed a THz-nano metasurface on silicon substrates to confine THz waves into nano-gaps (15 nm, λ/33,000), achieving local field enhancement.
• * Investigated carrier dynamics using 800 nm optical injection to observe strong-field induced effects.

Main Results:

• * Successfully demonstrated nonlinear modulation dynamics of the THz-nano metasurface.
• * Observed a self-modulation frequency shift of approximately 50 GHz by tuning the THz field strength.
• * Attributed the phenomenon to impact ionization (IMI) in the silicon substrate and strong-field induced intervalley scattering (IVS).

Conclusions:

• * The THz-nano metasurface provides a robust platform for ultrafast, nanoscale strong-field THz-matter interactions.
• * The findings offer new avenues for THz nonlinear modulation device development.
• * This research paves the way for advancing THz science and applications in accessible laboratory environments.