This work suggests an unconventional spectroscopic method for high sensitivity material characterization in the THz regime. This unique method was aimed to combine 3D printing, THz waveguides while it detects the THz electric field from the surface of the waveguide with a flexible detector based on graphene.
First, we investigated the design and fabrication of the 3D printed waveguide spectrometer (3DTera-WaSp), which will consist of a waveguide 3D-printed with cyclic olefin copolymer (COC), a polymer transparent in both the THz and optical regime with low absorption. Then, the waveguides were simulated using COMSOL Multiphysics and the Radio Frequency module (fig.1). For the 3D printing of the waveguides, the optimized parameters were used Bed temperature: 90 oC, nozzle size: 150 μm, printing temperature: 260 oC, and printing speed: 2000 mm/min (fig. 2). In addition, we explored graphene transfer on TOPAS, which was confirmed by Raman spectroscopy (fig. 3).
Fig. 1. a) Schematic representation of the waveguide where τ is the cladding thickness and D the diameter of the pipe waveguide. b) Comsol simulations of the waveguide with fundamental frequency core mode f=350 GHz.
Fig. 2. 3D printed THz pipe waveguides.
Figure 3. a) Raman spectrum of graphene on TOPAS. The G′band at about 2700 cm-1 and 1580cm-1 are apparent. b) Microscope image of graphene on TOPAS after the transfer. c) IV curve that shows that the graphene on TOPAS is conductive. d) Microscope image of part of the antennas fabricated on graphene with TOPAS substrate. The sample was used for the measurement of the IV curve.
PublicatIons and conference contributions
Optimized 3D printing of THz waveguides with cyclic olefin copolymer, E. Mavrona, J. Graf, E. Hack, P. Zolliker, Optical Materials Express 11 (8), 2495-2504
Towards high quality 3D printed THz devices with cyclic olefin polymer, E. Mavrona, J. Graf, E. Hack, P. Zolliker, 45th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz), IEEE, 2020