Cutting-Edge THz Polarisation Multiplexer for 6G Networks

Researchers in Australia have made a groundbreaking advancement in terahertz communications by developing the first ultra-wideband integrated terahertz polarization (de)multiplexer on a substrateless silicon base specifically designed for 6G links. This innovative device, created at the University of Adelaide, operates in the sub-terahertz J-band from 220GHz to 330 GHz, catering to the demands of 6G communications and beyond.

Unlike existing planar multiplexers, this new device offers an ultrawide band for terahertz communications, addressing the limitations of previous technologies. By utilizing tapered directional couplers and air-silicon effective media integrated monolithically on a compact footprint, the substrateless all-silicon polarization multiplexer achieves remarkable performance metrics.

The device boasts a 37.8% fractional bandwidth, an average insertion loss of ≈1 dB, and a polarization extinction ratio above 20 dB over the 225–330 GHz range. These impressive results are attributed to the anisotropy of the effective cladding, which impacts the two orthogonal guided modes differently, enhancing overall efficiency.

Professor Withawat Withayachumnankul, from the School of Electrical and Mechanical Engineering at the University of Adelaide, highlighted the significance of this innovation, stating, “Our proposed polarisation multiplexer will allow multiple data streams to be transmitted simultaneously over the same frequency band, effectively doubling the data capacity.”

Moreover, the device's large relative bandwidth sets a new record for integrated multiplexers across all frequency ranges. Professor Withayachumnankul emphasized the potential scalability of this technology to cover all optical communications bands, showcasing its versatility and broad applicability.

The polarization multiplexer was meticulously fabricated using a deep reactive-ion etching (DRIE) process with a 250-μm high-resistivity intrinsic float-zone silicon wafer. The fabrication process involved precise photolithography techniques to define hole sizes and tapered directional couplers, ensuring accuracy and reliability in the device's performance.

Despite minor imperfections in the fabrication process, such as tapered holes and blind holes in the claddings, the device maintained high performance levels, underscoring the robustness of the effective medium utilized in its construction.

Dr. Weijie Gao, a postdoctoral researcher who collaborated on the project, conducted real-time HD-video transmission at 300 GHz using the polarizer. The setup involved optical beat signal generation, modulation, and transmission through a terahertz hollow-core fiber, showcasing the practical applications of the polarization multiplexer in high-speed data transmission.

Dr. Gao emphasized the transformative impact of this technology on terahertz communication systems, envisioning enhanced efficiency and reliability in high-speed wireless networks. The polarisation multiplexer is poised to drive advancements in various fields, including high-definition video streaming, augmented reality, and the evolution of next-generation mobile networks like 6G.

Looking ahead, Professor Masayuki Fujita, a co-author of the research, anticipates further exploration of applications and technology refinements in the coming years. He envisions widespread adoption and integration of terahertz technologies across industries, revolutionizing telecommunications, imaging, radar systems, and the internet of things within the next decade.

For more information, visit www.adelaide.edu.au.