Mateusz Surma
supervisor: Maciej Sypek
The development of terahertz sources and detectors allows for designing more complicated optical systems, including dedicated passive optical elements. Diffractive structures tend to be much thinner than refractive elements, introducing less attenuation. Shapes of diffractive structures are limited by the manufacturing method. For this reason, diffractive structures allow for a generation of a wide variety of intensity distributions. One of the specific tasks that passive optical elements may realize is a generation of uniform sample illumination. The following paper presents diffractive elements - holograms - forming uniform illumination at a particular plane. The radiation transformed by them forms a square area at the desired plane. The optimization method for phase modulation generation uses an iterative algorithm. Multiple different designs for phase modulation with a division of modulation area have been simulated, implemented and tested. The design frequency was 260 GHz selected due to available sources and detectors. Solutions giving the best results in numerical simulations have been manufactured. Then, diffractive optical structures were modeled and 3D printed. Styrene-butadiene copolymer (SBC) was selected as a printing material due to its good terahertz optical properties (refractive index: 1.557 and absorption coefficient: 0.18 cm-1 @ 260 GHz). Produced structures have been experimentally verified and the results compared with numerical calculations.