New silicon chip developed for 6G network

Gandhinagar: Achieving a significant milestone for future 6G wireless technology, scientists at the Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR) have developed an innovative silicon chip. Researchers at this autonomous institution of the Department of Science and Technology (DST) have proven that terahertz waves can be transmitted with very little loss even when obstacles are present. This innovation could prove to be a cornerstone for future compact terahertz circuits.

According to a PIB report, 6G networks are expected to use terahertz frequencies, which lie between microwave and infrared light. This frequency provides massive bandwidth, but guiding it in circuits is challenging. Typically, bends or junctions in a waveguide scatter or reflect the signal, causing it to weaken. The researchers created a photonic crystal by precisely arranging triangular holes in a silicon slab, which guides terahertz waves along the boundary of two regions. These boundary channels protect against backscattering.

The research team designed a silicon photonic crystal with a structure similar to the honeycomb lattice of graphene. They created an obstacle by changing the size of the triangular holes in a short section of the waveguide. During experiments, it was found that adding one obstacle caused only 1-2% loss and two obstacles caused only 2-3% loss. These results are extremely positive compared to conventional non-topological waveguides. Data transmission reached 100 gigabits per second (Gbit/s), meaning a 5 gigabyte high-definition film could be transferred in less than half a second.

The team tested three devices on high-resistivity silicon. The first device had two obstacles in series, the second had an omega-shaped path with four sharp bends and one central obstacle, and the third had a power splitter. Measurements in the 310-360 GHz range were consistent with simulations. Both output signals in the splitter were nearly identical, showing that the obstacle had minimal impact on transmission. In high-speed data tests, the double-barrier and omega-shaped devices achieved speeds of 48 and 60 Gbit/s, respectively. The splitter achieved a speed of 100 Gbit/s using QAM-32 modulation.

This study was led by Assistant Professor Dr. Abhishek Kumar of the Meta Optics Laboratory (MetoLab) at JNCASR. He stated, "Terahertz waves can cross an obstacle created by changing the hole geometry and carry 100 Gbit/s of data, making this effect a useful design tool for terahertz chips." Samina Mulla and Sangram Kumar Sahoo of JNCASR were joint first authors in this research. Additionally, experts from JNCASR, IISER Kolkata, IIT Bombay, A*STAR Institute of Microelectronics in Singapore, and the University of Lille in France collaborated. This work has been published in the journal 'Advanced Materials'.

In the future, the team plans to tune these obstacles electrically, thermally, or mechanically, making it possible to route signals along different paths as needed. This technology will be helpful in routing and splitting signals on a single chip.

The Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR) was a leading research institution under the Department of Science and Technology, Government of India. It was known for advanced research and development in various scientific fields, which contributed significantly to technological progress in the country.