Complex optical properties of polymeric composite materials mixed with quartz powder and investigated by THz time-domain spectroscopy

With the rapid development of terahertz (THz) technology comes the need to further explore the prospects for various applications of THz systems. Due to the strong need, components and equipment involving the exploration are indispensable. In order to find the most suitable material for THz technology, we selected three common materials for different 3D printing techniques—polyamide (PA), polylactic acid (PLA), and light-curable resin. After mixing each material with a quartz powder of a different weight percentage, we observed the change in absorption coefficients and refractive indices of the mixtures by THz time-domain spectroscopy (THz-TDS). The higher the ratio of a quartz powder to a mixture was, the smaller the absorption coefficient of the mixture would be. The optimum rate of change in the absorption coefficient was attained when the weight percentage of a quartz powder in a mixture was 50 wt%. At 1 THz of the measurement of THz-TDS, the average reduction in the absorption coefficients of the three different materials mixed respectively with a 50 wt% quartz powder was 39.17%. Besides reduced absorption coefficients, the mixtures’ refractive indices also changed as the weight percentage of a quartz powder in the mixtures varied. The PLA-based sample mixed with a 50 wt% quartz powder had the highest increase in the refractive index. Mixing quartz powders with materials, therefore, is an effective method to increase refractive indices and decrease absorption coefficients. The method can be applied in 3D printing techniques in the future to enhance the efficiency of THz components manufactured with 3D printing techniques.