New class of light wave discovered

Physicists from the ARC Centre of excellence for Ultrahigh bandwidth Devices for Optical Systems (CUDOS) have made a remarkable new discovery that opens up future applications in many areas such as in precision laser surgery, imaging devices, and ultrafast computing and communication technology.

Observed in nature; in tidal bores, rogue waves and electrical pulses in the human body, the soliton (a wave that maintains its shape as it travels over long distances) was first discovered in 1834 by Scottish engineer John Scott Russell.

Watching a wave created by a boat stopping in a narrow canal, he noted that it travelled for miles without breaking up – the shape of the canal creating a ‘self-reinforcing single wave’. Regular waves breakdown and flatten out, but solitons, whether they are made of water or light, continue on and hold their shape.

Since its discovery, physicists have been fascinated by the phenomenon and optical solitons, in particular, have been the subject of intense research over the past few decades due to their intriguing physics and applications in ultrafast optics and supercontinuum generation.

Until now, it was generally assumed that everything that could be known about solitons, had already been discovered. Today, CUDOS physicists have added a new chapter in the history of solitons. In their paper published in Nature Communications, the researchers lead by Dr Andrea Blanco-Redondo, detail their discovery of an entirely new class of optical soliton called pure-quartic solitons.

During their experiments, researchers found that pure-quartic solitons have remarkable properties compared to conventional ones - they have a different shape and can be more energetic than previously reported solitons. They also evolve in a different way and occur at different power thresholds.

These properties can turn them into excellent candidates to be used in a number of important applications which the CUDOS team are currently exploring. Enabled by precise dispersion engineering in photonic crystals that are etched into silicon photonic chips, pure-quartic solitons could find applications in ultrahigh bandwidth communications, frequency combs, and high-power ultra-fast lasers, such as those used in surgery.

“We discovered this new class of optical soliton when we were looking for experimental realisations of conventional solitons in silicon, which reminds us that, in science, we always have to keep our eyes open and our mind free of prejudices. We are very excited to keep unveiling the details and applications of this finding,” said Dr Blanco-Redondo.

CUDOS Director, Professor Benjamin J. Eggleton, co-author on the paper, added that the discovery was possible because researchers experimented on a silicon photonic chip, “The unique features of the silicon chip provides conditions that were not previously accessible, and now opens up a whole new regime for soliton experimentation.”

This important discovery was a result of the collaboration by CUDOS (The University of Sydney), the University of Toronto, and the University of York.