3D-printed phase waveplates for THz beam shaping

The advancement of 3D-printing opens up a new way of constructing affordable custom terahertz (THz) components due to suitable printing resolution and THz transparency of polymer materials. We present a way of calculating, designing, and fabricating a THz waveplate that phase-modulates an incident THz beam (λ₀ = 2.14 mm) in order to create a predefined intensity profile of the optical wavefront on a distant image plane. Our calculations were performed for two distinct target intensities with the use of a modified Gerchberg-Saxton algorithm. The resulting phase-modulating profiles were used to model the polylactide elements, which were printed out with a commercially available 3D-printer. The results were tested in a THz experimental setup equipped with a scanning option, and they showed good agreement with theoretical predictions.