Fig. 1. Scanning imaging with THz Gaussian and Bessel beams[9-10]. (a) Imaging system based on broadband THz Gaussian beam; (b) imaging system based on THz Bessel beam; (c)(e)(g) THz intensity images of object at 30, 40, and 50 mm from objective lens; (d)(f)(h) THz intensity images of object at 30, 40, and 50 mm from axicon; (i) lion effigy; (j) transmitted phase image of lion effigy measured by THz Bessel beam; (k) transmitted phase image of lion effigy measured by THz Gaussian beam; (l) reconstructed

Fig. 2. Vectoral characterization of THz Bessel beam by using THz digital holographic imaging system[11]. (a) Imaging system and sample; (b) transverse amplitude pattern of Ex with 0.6 THz at 12 mm and longitudinal amplitude pattern on cross-section of y=0 mm; (c) corresponding transverse and longitudinal phase patterns of Ex; (d) transverse and longitudinal amplitude patterns of Ez with 0.6 THz at 12 mm; (e) transverse and longitudinal phase patterns of Ez on cross-section of y=0 mm

Fig. 3. Generation and polarization modulation of THz surface plasmon Bessel beam (TSPBB)[12]. (a) Schematic of slit array of rectangular antenna; (b) intensity patterns of TSPBB with zeroth-order at 0.75 THz for horizontal and vertical polarized incident beams; (c) intensity patterns of TSPBB with first-order at 0.75 THz for horizontal and vertical polarized incident beams; (d) intensity patterns of TSPBB excited by left-circularly polarized incident beams; (e) intensity patterns of TSPBB excited by ri

Fig. 4. Generation and analysis of THz vortex beam based on meta-surface technique[13]. (a) THz vortex phase plate based on V-shaped metallic antenna; (b) THz digital holographic imaging system; (c) measured THz amplitude patterns; (d) measured THz phase patterns; (e) simulated phase patterns of THz vortex beam on different observation planes

Fig. 5. Vectoral characteristics of THz converging vortex beams[14]. (a) Polylactic vortex phase plates ; (b) THz digital holographic imaging system; (c) amplitude and phase patterns of Ex at 0.62 THz on focal plane for linearly polarized THz vortex beam with l=1; (d) amplitude and phase patterns of Ex with l=2; (e) amplitude and phase patterns of Ez for linearly polarized THz vortex beam with l=1; (f) amplitude and phase patterns of Ez with l=2; (g) amplitude and phase patterns of Ez for circularly pol

Fig. 6. Generation and analyses of THz vortex Bessel beams[15]. (a) THz imaging system, vortex phase plate, and axicons; (b) amplitude patterns of Ex on transverse and longitudinal cross-sections at z=4, 8, 12, 16, 20 mm; (c) corresponding phase patterns of Ex on transverse and longitudinal cross-sections; (d) amplitude patterns of Ez on transverse and longitudinal cross-sections at z=4, 8, 12, 16, 20 mm; (e) corresponding phase patterns of Ez on transverse and longitudinal cross-sections

Fig. 7. Multiplexed sub-THz communications with dual OAM mode antenna[16]. (a)(b) Schematic and photo of dual OAM mode antenna; (c)(d) sub-THz amplitude and phase patterns with l=+3 and frequency of 60 GHz radiated by antenna; (e)(f) sub-THz amplitude and phase patterns with l=-3 radiated by antenna; (g) schematic of dual-channel communications with OAM mode antenna; (h) temporal signals measured by l=+3 and l=-3 receivers

Fig. 8. Generation and characterization of THz ring-Airy beam[17]. (a) Designed ring-Airy meta-hologram device with optical microscope image of partial sample in inset; (b) THz digital holographic imaging system; (c) experimental and (e) simulated intensity patterns of spectral component at 0.8 THz on exit surface of sample; longitudinal intensity patterns of THz ring-Airy beam at 0.8 THz extracted from (d) experiment and (f) simulation

Fig. 9. Generation and analysis of THz Airy vortex beam (TAVB)[18]. (a) Schematic of experimental setup for generating TAVBs(upper inset: photos of 3D-printed phase plates R1 and R2, lower inset: intensity pattern of incident THz beam); (b) propagation processes of TAVBs with topological charges of l=0-3 on x-z plane; (c) intensity patterns of TAVBs with various topological charges at z=0 mm and z=100 mm

Fig. 10. Generation and characterization of THz bottle beam[19]. (a) THz characterization system and samples; (b) THz amplitude images on x-y plane at z=-4.5, 0, 4.5 mm; (c) longitudinal amplitude cross-section of THz field on x-z plane; (d)(e) THz phase patterns on transverse and longitudinal cross-sections

Fig. 11. Generation and characterization of radially polarized THz beam[20]. (a) Experimental amplitude and phase patterns on different polarization orientations for radially polarized THz beam; (b) corresponding simulation results

Fig. 12. Generation and application of THz radially polarized beam[21-22]. (a) Schematic and photo of segmented nonlinear optical crystal with threefold rotational symmetry; (b) THz intensity images projected along x, y, and 45° polarization orientations for THz radially, azimuthally, and x-linearly polarized beams; (c) schematic of THz linear electron accelerator; (d) electron density distribution images as well as electron energy spectra recorded by micro-channel plate without THz field (left) and with