Smaller, faster and more efficient modulator sets to revolutionize optoelectronic industry

September 24, 2018, City University of Hong Kong
The new tiny modulator drives data at higher speeds and lower costs. Credit: Second Bay Studios/Harvard SEAS

A research team comprising members from City University of Hong Kong (CityU), Harvard University and a renowned information technologies laboratory has successfully fabricated a tiny on-chip lithium niobate modulator, an essential component for the optoelectronic industry. The modulator is smaller, more efficient with faster data transmission, and costs less. The technology is set to revolutionise the industry.

The electro-optic produced in this breakthrough research is only 1 to 2 cm long and its surface area is about 100 times smaller than traditional ones. It is also highly efficient—higher data transmission speed with data bandwidth tripling from 35 GHz to 100 GHz, but with less energy consumption and ultra-low optical losses. The invention will pave the way for future high-speed, low power and cost-effective communication networks as well as quantum photonic computation.

The research project is titled "Integrated lithium niobate electro-optic modulators operating at CMOS-compatible voltages," and was published in the latest issue of Nature.

Electro-optic modulators are critical components in modern communications. They convert high-speed electronic signals in computational devices such as computers to optical signals before transmitting them through optical fibres. But the existing and commonly used lithium niobate modulators require a high drive voltage of 3 to 5V, which is significantly higher than 1V, a voltage provided by a typical CMOS (complementary metal-oxide-semiconductor) circuitry. Hence an electrical amplifier that makes the whole device bulky, expensive and high energy-consuming is needed.

Dr. Wang Cheng, Assistant Professor in the Department of Electronic Engineering at CityU and co-first author of the paper, and the research teams at Harvard University and Nokia Bell Labs have developed a new way to fabricate lithium niobate modulator that can be operated at ultra-high electro-optic bandwidths with a voltage compatible with CMOS.

"In the future, we will be able to put the CMOS right next to the modulator, so they can be more integrated, with less power consumption. The electrical amplifier will no longer be needed," said Dr. Wang.

Thanks to the advanced nano fabrication approaches developed by the team, this modulator can be tiny in size while transmitting data at rates up to 210 Gbit/second, with about 10 times lower optical losses than existing modulators.

"The electrical and optical properties of lithium niobate make it the best material for modulator. But it is very difficult to fabricate in nanoscale, which limits the reduction of modulator size," Dr. Wang explains. "Since lithium niobate is chemically inert, conventional chemical etching does not work well with it. While people generally think physical etching cannot produce smooth surfaces, which is essential for optical transmission, we have proved otherwise with our novel nano fabrication techniques."

With optical fibres becoming ever more common globally, the size, the performance, the power consumption and the costs of modulators are becoming a bigger factor to consider, especially at a time when the data centres in the information and communications technology (ICT) industry are forecast to be one of the largest electricity users in the world.

This revolutionary invention is now on its way to commercialisation. Dr. Wang believes that those who look for modulators with the best performance to transmit data over long distances will be among the first to get in touch with this infrastructure for photonics.

Dr. Wang began this research in 2013 when he joined Harvard University as a Ph.D. student at Harvard's John A. Paulson School of Engineering and Applied Sciences. He recently joined CityU and is looking into its application for the coming 5G communication together with the research team at the State Key Laboratory of Terahertz and Millimeter Waves at CityU.

"Millimetre wave will be used to transmit data in free space, but to and from and within base stations, for example, it can be done in optics, which will be less expensive and less lossy," he explains. He believes the invention can enable applications in quantum photonics, too.

Professor Marko Lončar and Dr. Zhang Mian at Harvard University are the corresponding author and another co-first author of the paper respectively. Other co-authors include Maxime Bertrand, Amirhassan Shams-Ansari from Harvard University, and Chen Xi, Sethumadhavan Chandrasekhar and Peter Winzer from Nokia Bell Labs.

Explore further: Big energy savings: Researchers build the world's smallest electro-optic modulator

More information: Cheng Wang et al, Integrated lithium niobate electro-optic modulators operating at CMOS-compatible voltages, Nature (2018). DOI: 10.1038/s41586-018-0551-y

Related Stories

Optoelectronics without glass

November 3, 2017

Researchers at ETH Zurich have developed the first opto-electronic circuit component that works without glass and is instead made of metal. The component, referred to as a modulator, converts electrical data signals into ...

Recommended for you

Supercomputers without waste heat

December 10, 2018

Generally speaking, magnetism and the lossless flow of electrical current ("superconductivity") are competing phenomena that cannot coexist in the same sample. However, for building supercomputers, synergetically combining ...

Engineers invent groundbreaking spin-based memory device

December 7, 2018

A team of international researchers led by engineers from the National University of Singapore (NUS) have invented a new magnetic device to manipulate digital information 20 times more efficiently and with 10 times more stability ...

Multichannel vectorial holographic display and encryption

December 7, 2018

Holography is a powerful tool that can reconstruct wavefronts of light and combine the fundamental wave properties of amplitude, phase, polarization, wave vector and frequency. Smart multiplexing techniques (multiple signal ...

A new 'spin' on kagome lattices

December 7, 2018

Like so many targets of scientific inquiry, the class of material referred to as the kagome magnet has proven to be a source of both frustration and amazement. Further revealing the quantum properties of the kagome magnet ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.