A New Ultra-High-Speed Terahertz Chip

A photonic topological insulator chip made from silicon, which can transmit terahertz waves at ultrahigh speeds. (Source: NTU)

To enable data transmission speeds that surpass the 5th Generation (5G) standards for telecommu­nications, scientists from Nanyang Techno­logical University, Singapore (NTU Singapore) and Osaka University in Japan have built a new chip using photonic topo­logical insulators. The researchers showed that their chip can transmit terahertz waves resulting in a data rate of 11 Gigabits per second (Gbit/s), which is capable of supporting real-time streaming of 4K high-definition video, and exceeds the hitherto theoretical limit of 10 Gbit/s for 5G wireless communi­cations.

Terahertz waves are part of the electro­magnetic spectrum, in between infrared light waves and microwaves, and have been touted as the next frontier of high-speed wireless communi­cations. However, fundamental challenges need to be tackled before terahertz waves could be used reliably in telecommu­nications. Two of the biggest issues are the material defects and trans­mission error rates found in conven­tional waveguides such as crystals or hollow cables.

These issues were overcome using Photonic Topo­logical Insulators (PTI), which allows light waves to be conducted on the surface and edges of the insulators, akin to a train following railroads, rather than through the material. When light travels along photonic topo­logical insulators, it can be redirected around sharp corners and its flow will resist being disturbed by material imperfections. By designing a small silicon chip with rows of triangular holes, with small triangles pointing in the opposite direction to larger triangles, light waves become topo­logically protected.

This all-silicon chip demons­trated it could transmit signals error-free while routing terahertz waves around 10 sharp corners at a rate of 11 gigabits per second, bypassing any material defects that may have been introduced in the silicon manu­facturing process. Leader of the project, Ranjan Singh, said this was the first time that PTIs have been realised in the terahertz spectral region, which proves the previously theo­retical concept, feasible in real life.

Their discovery could pave the way for more PTI terahertz inter­connects – structures that connect various components in a circuit – to be integrated into wireless communication devices, to give the next generation 6G communi­cations an unpre­cedented terabytes-per-second speed (10 to 100 times faster than 5G) in future. “With the 4th industrial revolution and the rapid adoption of Internet-of-Things (IoT) equip­mentsmart devices, remote cameras and sensors, IoT equipment needs to handle high volumes of data wirelessly, and relies on communi­cation networks to deliver ultra-high speeds and low latency,” explains Singh.

“By employing terahertz technology, it can potentially boost intra-chip and inter-chip communication to support Artificial intelli­gence and cloud-based technologies, such as inter­connected self-driving cars, which will need to transmit data quickly to other nearby cars and infra­structure to navigate better and also to avoid accidents”, Singh added.

This project took the NTU team and their colla­borators led by Masayki Fujita at Osaka University two years of design, fabrication, and testing. Singh believes that by designing and producing a minia­turised platform using current silicon manu­facturing processes, their new high-speed terahertz interconnect chip will be easily integrated into electronic and photonic circuit designs and will help the widespread adoption of Terahertz in future. Areas of potential application for terahertz inter­connect technology will include data centres, IOT devices, massive multicore CPUs (computing chips) and long-range communi­cations, including telecommu­nications and wireless communi­cation such as Wi-Fi. (Source: NTU)

Reference: Y. Yang et al.: Terahertz topological photonics for on-chip communication, Nat. Phot. 14, 446 (2020); DOI: 10.1038/s41566-020-0618-9

Link: Centre for Disruptive Photonic Technologies, The Photonics Institute, Nanyang Technological University, Singapore, Singapore

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