Generating Angular-Varying Time Delays of THz Pulses via Direct Space-to-Time Mapping of Metasurface Structures

Abstract

We experimentally demonstrate the generation of double terahertz (THz) pulses with tailored angular-dependent time delays from a nonlinear metasurface excited by a near-infrared femtosecond pulse. The tailored temporal properties of the generated pulses emerge from a direct mapping of the nonlinear spatial response of the metasurface to the emitted THz temporal profile. We utilize the Pancharatnam-Berry phase to implement symmetric and antisymmetric metasurface configurations and show that the emitted patterns present spatiotemporal “X-shaped” profiles after collimation by a parabolic mirror, with angular-dependent pulse delays corresponding to the intended design. In addition, we show that the addition of polarization multiplexing presents the opportunity to achieve a full range of elliptical THz polarizations. Double pulse generation and spatiotemporal shaping of THz waves in general show potential for THz spectroscopy and molecular dynamics applications, particularly in pump–probe experiments.

Spatiotemporal modulation of ultrafast plasmonic vortices with spin–orbit coupling

“…In ultrafast optical information processing, some previous works have demonstrated that ultrafast time-varying effects induced by two time-delayed femtosecond pulses can be used in the fields of optical switching, time-varying holographic imaging, and beam modulation. Here the time-varying OAM of femtosecond SPP vortex can also be used in ultrafast switching of optical information [47,48], especially with the nonlinear materials or with OAM-multiplex structures.…”