Terahertz vector beam generation using structured metallic gratings

This work details the laser fabrication of various metallic gratings to develop terahertz (THz) optics capable of creating spatially varying THz vector beams. The output beam from fabricated copper gratings of differing geometries is characterized experimentally by examining the output intensity and polarization state distribution and compared with simulations from a recent study [M. Cai et al., Opt. Express, 32, 33357, (2024)10.1364/OE.530489]. A THz time-domain spectroscopy system is configured in a polarimetric scanning configuration to measure the spatially resolved and spectrally encoded Jones matrix of each fabricated grating and to determine the output fields. Radial and azimuthal THz vector fields are successfully generated, demonstrating successful spatial polarization manipulation of the broadband THz beam. Intensity profiles are also imaged and confirmed with a polarization-resolved 0.29 THz single-pixel (compressive) imaging system for experimental completeness. Frequency dependencies of an output spiral-shaped THz vector beam are studied from 0.10-0.50 THz, over which, successful spatial polarization modulation of the THz beam occurs. These findings provide the necessary experimental insight into the feasibility of laser-fabricated optics for THz vector beam generation and will be beneficial to researchers of applications, including THz imaging microscopy and THz communications.