Quasi-optical components for the THz-regime: Fabrication and characterization

Computational Shear-interferometry (CoSI) has recently been used in the visible band of the electromagnetic spectrum for wave field sensing. Extending this concept into the THz-regime would allow broadening the concept of wave field sensing into this band. Yet, one has to fabricate, characterize and evaluate quasi-optical components suitable for the THz-regime. In this paper, we demonstrate the construction of lenses with different focal lengths and Ronchi phase gratings with different periods and heights. For this purpose, we use two different fabrication schemes: Firstly, mechanical milling from bulk High-Density Polyethylene (HDPE-block) using a computer numerical control (CNC) machine, and secondly, 3D printing of polystyrene and TOPAS copolymer will be compared. For the characterization, we use a tactile probe for measuring the radius of curvature of the lenses and a scanning confocal microscope for measuring the period and the height of the phase Ronchi gratings. The measured radius of curvature of the lenses deviates about 0.23% from the design value while the grating period length and the height profile are fabricated with ±50 µm and ±25 µm precision, respectively.