A new on-chip microcomb to synchronize signals in optoelectronics

Optoelectronics are promising devices that combine optical components, which operate leveraging light, with electronics, which leverage electrical current. Optoelectronic systems could transmit data faster than conventional electronics, thus opening new possibilities for the development of high-speed communication technology.

Despite their potential, the deployment of optoelectronics has so far been limited, in part due to reported difficulties in synchronizing optically generated signals with those of traditional electronic clocks. These signals are difficult to synchronize as optical and electronic components typically operate at different frequencies.

The frequencies of optical signals (i.e., generally hundreds of gigahertz) are generally significantly higher than those of electronic circuits, which range from megahertz to a few gigahertz. This mismatch in frequencies makes aligning the frequencies of the two types of components challenging, which in turn adversely impacts the reliability and efficiency of optoelectronics.

Researchers at Peking University, the Chinese Academy of Sciences and other institutes recently developed a new on-chip microcomb, a small optical device that can generate a precise series of equally spaced frequencies spanning across different wavelengths.

This device, outlined in a paper published in Nature Electronics, could serve as a precise clock for both optical and electronic components, synchronizing signals across a wide range of frequencies.

"Optoelectronics could be used to develop fast and wideband information systems," Xiangpeng Zhang, Xuguang Zhang and their colleagues wrote in their paper. "However, the large frequency mismatch between optically synthesized signals and electronic clocks makes it difficult to synchronize optoelectronic systems.

"We describe an on-chip microcomb that can synthesize single-frequency and wideband signals covering a broad frequency band (from megahertz to hundreds of gigahertz) and that can provide reference clocks for the electronics in the system."

Compared to other previously proposed approaches to synchronize signals in optoelectronics, the microcomb developed by the researchers does not require so-called coherent digital signal processing. This is a method to correct mismatches in software, which is known to be computationally demanding and thus not ideal for practical applications.

"Our synchronization strategy, which aligns optically synthesized signals and electronics, can provide signal manipulation precision and data transmission without coherent digital signal processing," wrote the researchers. "To illustrate the capabilities of this approach, we create a wireless joint sensing and communication system based on a shared microcomb-based transmitter."

To assess the potential of their microcomb, the team used it to develop a new optoelectronic wireless device that could be used both for sensing and communications. In this system, the microcomb served as a transmitter, facilitating data transmission and remote sensing.

The findings of the team's evaluation were promising, yet their microcomb could soon be improved further. Using photodetectors with larger bandwidths, for instance, the microcomb could generate frequencies spanning across the entire microwave and terahertz frequency bands.

A key advantage of the new device created by the researchers is that it enables high repetition rates, while also consuming less power than conventional electronic synchronization approaches. In the future, the microcomb could be improved further and used to synchronize signals in other optoelectronic systems, potentially contributing to their future widespread adoption.

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