Fig. 1. (a) Lens for quasi-nondiffractive OAM waves, and the picture is quoted from Ref. [11], (b) nondiffractive Bessel beam launcher, and the picture is quoted from Ref. [21], (c) flat-top beam shaper, and the picture is quoted from Ref. [12], (d) Luneburg lens, and the picture is quoted from Ref. [22], (e) LP-CP converter, and the picture is quoted from Ref. [24], (f) polarization beam splitter, and the picture is quoted from Ref. [25]

Fig. 2. (a-ⅰ) 3-D near-field focus-scanning lens, (a-ⅱ) power densities on the three focal planes (S = 0.5, 4.5, and 8.5 mm) at 300 GHz by combining synchronous co-rotation and counter-rotation of the lenses, and the picture is quoted from Ref. [10], (b) multi-focus lens, and the picture is quoted from Ref. [43], (c-ⅰ) stretchable Fresnel flat zone plate, (c-ⅱ) Fresnel flat zone plate at stretching degrees of 0 and 21%, (c-ⅲ) E-field of the zone plate at stretching degrees of 0 and 21%, and the picture is quoted from Ref. [44], (d) two-layered cascaded discrete dielectric lens, and the picture is quoted from Ref. [17], (e-ⅰ) high numerical aperture metalens, (e-ⅱ) the schematic diagram of processing flow of metalens, and the picture is quoted from Ref. [45], (f) measurement setup of the time domain spectrometer , and the picture is quoted from Ref. [55], (g) measurement setup of the Field-effect transistors, and the picture is quoted from Ref. [18]

Fig. 2. (a) Bullet shaped ceramic composite lens, and the picture is quoted from Ref. [26], (b) hyperhemispherical Si lens, and the picture is quoted from Ref. [27], (c) hemicylindrical PTFE lens^[16], (d) hemispherical TPX, and the picture is quoted from Ref. [13], (e) cylindrical sapphire-fiber lens, and the picture is quoted from Ref. [29], (f) 3D printed planar lens, and the picture is quoted from Ref. [30]

Table 1. THz lens antennas for beam control in references

Table 2. High gain THz lens antennas in references

Table 3. THz lens antennas for focus and collimation