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Nature Electronics features Southampton Silicon Photonics Group breakthrough in data transmission

Published: 15 January 2024

Southampton Silicon Photonics group's ground-breaking research was recently published in the prestigious Nature Electronics journal. The paper, titled ''An integrated CMOS-silicon photonics transmitter with a 112 gigabaud transmission and picojoule per bit energy efficiency,' showcases impressive performance and efficiency gains achieved through the co-design and integration of a silicon photonic modulator and complementary metal-oxide-semiconductor (CMOS) electronic drive amplifier.

Professor David Thomson from the Optoelectronics Research Centre (ORC) said: "Silicon optical modulators are used to convert electrical signals into optical signals, but there is a limit to the speed at which they can effectively operate. The challenge lies in the trade-off between the speed and drive power requirements, forcing a choice or compromise between the two parameters."

He added: "Our breakthrough involves the development of an integrated transmitter that synergistically combines electronics and photonics, showcasing superior performance compared to individual devices. For example, the CMOS electronic driver chip was designed in conjunction with a low-power modulator to address its bandwidth limitations, such that when combined a higher speed of operation is possible than from the modulator alone, therefore optimising overall performance. This co-designed approach, merging the modelling process of the optical modulator and its electronic drive amplifier, has enabled breakthroughs in speed and power consumption."

Implementing their innovative design strategy, the researchers created a transmitter capable of operating at 112 gigabaud, allowing 112 gigabits per second data transmission with on-off keying and 224 gigabits per second using pulse-amplitude modulation (PAM-4). Remarkably, the energy consumption of the device was recorded below a picojoule per bit, showcasing its efficiency.

David went on to discuss alternative research directions: "Until recently silicon based optical modulators were thought to have reached the limit of their operating performance. This has led other researchers to look at the integration of exotic materials – such as lithium niobate – with silicon waveguides for improved modulator performance." However, he noted that such integration compromises CMOS compatibility, complicating routes for high-volume, high-yield and low-cost manufacturing.

He emphasized: "Our research demonstrates that there are still avenues to enhance the performance of all-silicon-based devices."

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