Terahertz Stepped-Height Waveguide With 3-D-Printing

At terahertz frequencies, where Ohmic losses are high, all-dielectric waveguides have emerged as the basis of low-loss integrated circuits. Usually, advanced foundry fabrication techniques are leveraged to realize these devices from semiconductor materials, such as silicon, owing to their high permittivities. However, these methods are restrictive when 2.5-D devices are desired, requiring multiple stages of masking and etching. Here, advances in ceramic 3-D printing are exploited to realize single-mode height-varying waveguides that operate over the WR3.4 band, from 220 to 330 GHz. The waveguide is experimentally characterized, showing attenuation on the order of 0.2 dB/cm (
$\pm1$
dB/cm), comparable to the ubiquitous hollow metallic waveguide at the same frequency range. Capitalizing on design freedom, we demonstrate a liquid-identifying application, using a ring resonator with an integrated well to hold the analyte. The extra design freedom afforded by 3-D printing combined with the properties of ceramics and robust performance of the waveguide lays the groundwork for future integrated passive devices with added functionality.