Time-resolved detection of terahertz response in photodynamically induced plasmonic metasurfaces

A modification of terahertz time-domain spectroscopy is proposed. It includes the direct measurement of the temporal profile of the transmitted terahertz pulse, the extraction of the pulse corresponding to multiple reflections from the object surfaces, and its analysis without the Fourier transform algorithm. The method is tested on one-dimensional gratings that are photodynamically induced on the gallium arsenide surface and support the excitation of collective plasmonic modes in the terahertz range. The suggested approach allows us to overcome the limitations typical of the conventional terahertz time-domain spectroscopy and expands the capabilities of the existing terahertz photonic instrumentation.