Characteristics of Effective-Medium-Clad Dielectric Waveguides

Effective-medium-clad dielectric waveguides are purely built into a single high-resistivity float-zone silicon wafer with their claddings defined by deep subwavelength perforations. The waveguides are substrate-free while supporting both E ^x ₁₁ and E ^y ₁₁ modes with low loss and low dispersion. This article extends the investigations of the waveguides by analyzing the dispersion, cross-polarization, and crosstalk together with the characteristics of bends and crossings over an operation frequency range of 220- 330 GHz (WR-3 band). Taking the E ^x ₁₁ mode as an example, the experimental results show an average measured attenuation coefficient of 0.075 dB/cm and a group velocity dispersion ranging from around ±10 ps/THz/mm across the whole band. A crosstalk level below -10 dB is measured for parallel waveguides with a separation of 0.52λ ₀ at 300 GHz. The realized waveguides show a bending loss ranging from 0.500 to 0.025 dB per bend and a crosstalk at crossing below -15 dB from 220 to 330 GHz. Due to the different dispersion characteristics, the E ^y ₁₁ mode has similar performances but with its operation frequency range reduced to 260-330 GHz. Limited by the measurement setup, a cross-coupling between the E ^x ₁₁ and E ^y ₁₁ modes is measured to be below -20 dB over the whole band. This in-depth investigation of effective-medium-clad waveguides will form a basis for terahertz-integrated platforms.