Mateusz Surma
supervisor: Maciej Sypek
The homogenous illumination finds its application mainly in imaging. One can obtain more uniform illumination in many ways. In the case of wideband illumination, one would usually use optimized refractive setups or micro-lens structures. For monochromatic sources, there is the possibility of using diffractive structures instead. Diffractive structures, compared with refractive, are thinner, resulting in smaller losses due to absorption – an essential feature for weaker THz sources. This paper describes an algorithm for optimizing holograms for homogeneous illumination based on the Ping-Pong algorithm and sub-division of phase modulation. The phase modulation was divided into four segments, each responsible for reconstructing the target at slightly different distances and put together in various combinations. Holograms were designed and simulated for 260 GHz (wavelength of ca 1.2 mm). Later structures were manufactured with fused deposition modeling 3D printing method with styrene-butadiene copolymer (BendLay by OrbiTech). The material was chosen based on good optical properties at the selected frequency. Prepared structures were tested in THz setup with a Schottky-diode-based multiplier chain used as the source and detector.