3D Printed Al2O3 for Terahertz Technology

In this work we demonstrate that 3D printed Al₂O₃ is a promising material for prototyping and precise fabrication of quasi-optical devices in the terahertz frequency range. The 3D printed Al₂O₃ exhibits a low absorption coefficient (<inline-formula> <tex-math notation="LaTeX">$\alpha < 2\textrm {cm}^{-1}$ </tex-math></inline-formula>at 1 THz) and a high refractive index (<inline-formula> <tex-math notation="LaTeX">$n >3$ </tex-math></inline-formula>). The printing resolution in the sub <inline-formula> <tex-math notation="LaTeX">$50~\mu \text{m}$ </tex-math></inline-formula> range allows for the implementation of structures in the 0.3-3.0 THz range on the subwavelength scale. Furthermore, the printing process enables the realization of crystalline solids, which allows the use of the Al₂O₃ birefringence effect. Here, a <inline-formula> <tex-math notation="LaTeX">$\Delta n \approx ~0.05$ </tex-math></inline-formula> was achieved and used for the implementation of <inline-formula> <tex-math notation="LaTeX">$\lambda $ </tex-math></inline-formula>/2-wave plates working at ~1 THz. The material properties and wave plates were characterized using a terahertz time-domain spectrometer.