Indian terahertz silicon devices reach 100 Gbit/s

By Elena Vasquez

Indian researchers have demonstrated silicon terahertz devices transmitting at up to 100 Gbit/s, while engineered barriers produced losses of about 1–2% for one barrier and 2–3% for two. The team says the compact components could serve as building blocks for future sixth-generation wireless networks, but the work has not reached an operator network.

Researchers at the Jawaharlal Nehru Centre for Advanced Scientific Research, an autonomous institute under India’s Department of Science and Technology, made the demonstration. Dr Abhishek Kumar, an assistant professor at JNCASR and head of its Meta Optics Laboratory, led the study.

How can terahertz signals cross a barrier?

Terahertz frequencies sit between microwaves and infrared light and offer wide bandwidth for high-speed wireless communication. Their challenge in compact circuits is that bends, junctions and other changes to waveguide geometry can scatter or reflect signals, reducing transmission efficiency.

The researchers built a silicon photonic crystal designed to mimic graphene’s honeycomb lattice. By arranging triangular holes in a carefully engineered pattern, they formed channels that guide terahertz waves along the boundary between two regions.

The team created barriers by changing the sizes of triangular holes over short sections of a waveguide. These structures exploit photonic Klein tunnelling, a phenomenon that allows waves to cross certain engineered barriers without significant reflection.

A single barrier produced around 1–2% signal loss, while two barriers in sequence resulted in approximately 2–3% loss. Transmission remained close to its barrier-free level as long as the barrier strength stayed below the photonic crystal’s characteristic coupling strength, providing a design principle for practical terahertz circuits.

What did the researchers build?

The team fabricated three devices using high-resistivity silicon, a material compatible with established semiconductor manufacturing processes. Each configuration tested a different way of routing or dividing terahertz signals:

• A double-barrier waveguide supported transmission at 48 Gbit/s.
• An omega-shaped route, featuring four sharp bends and a central barrier, supported 60 Gbit/s.
• A power splitter, with a barrier in one of its two output branches, reached 100 Gbit/s using QAM-32 modulation.

Measurements across frequencies of 310–360 GHz closely matched the researchers’ computer simulations. The power splitter also produced nearly identical signals at its two outputs, indicating that the engineered barrier had little effect on transmission.

QAM-32 encodes information through variations in a signal’s amplitude and phase. The three data rates therefore came from separate devices and configurations, rather than from one circuit delivering all three speeds.

What happens before 6G deployment?

Samina Mulla and Sangram Kumar Sadhu were joint first authors, with collaborators from institutions in India, Singapore and France. The team published its findings in Advanced Materials.

The paper identifies compact terahertz circuits that can route and split high-frequency signals with limited loss as the practical goal. It does not describe an operator trial, a commercial product or a deployment timetable, leaving the evidence firmly at component level.

The researchers plan to investigate electrical, thermal and mechanical control of the engineered barriers. If the team can vary those barriers reliably, signals could eventually be redirected between different paths on a chip on demand.

Further development will be needed before the devices can enter operational 6G communication systems. The next milestone is therefore experimental rather than commercial: demonstrating dependable control of the barriers before moving toward system-level 6G trials.