Figure 2
From: Fabricating THz spiral zone plate by high throughput femtosecond laser air filament direct writing
(a) Optical image of the SZP with l = 0 fabricated by femtosecond laser filament; (b) schematic diagram of the measurement locations of the THz intensity distributions near the SZP’s image plane; (c–e) measured intensity distributions of the THz beam at three different positions (P1–P3); (f) experimental and theoretical radial intensity profiles of the THz beam at the SZP’s image plane.
