UK scientists have created an 'eternal engine' to keep the next generation of atomic clock ticking.

Atomic clock precision timing is essential for systems such as global navigation, satellite mapping, establishing the composition of exoplanets and the next generations of telecommunication.

Now, research undertaken at the University of Sussex, and continued at Loughborough University, has solved a major stumbling block in the development of these portable atomic clocks, by working out how to reliably switch 'on' their counting device - and keep them running.

Microcombs are a fundamental part of future optical atomic clocks - they allow one to count the oscillation of the 'atomic pendulum' in the clock, converting the atomic oscillation at hundreds of trillions of times per second to a billion times a second - a gigahertz frequency, that modern electronic systems can easily measure.

Based on electronic compatible optical microchips, microcombs are the best candidates to miniaturise the next generation of ultraprecise timekeeping.

"A well-behaved microcomb uses a special type of wave, called a cavity-soliton, which is not simple to get. Like the engine of a petrol car, a microcomb prefers to stay in an 'off-state'. When you start your car, you need a starter motor that makes the engine rotate properly."

"Professor Marco Peccianti, who worked on the research at the University of Sussex and directs the newly funded Emergent Photonic Research Centre at Loughborough University, added:"In 2019 we had already demonstrated that we could use a different type of wave to get microcombs.

"Dr Maxwell Rowley, who obtained his PhD at the University of Sussex developing this system with Prof Pasquazi, and who now works with CPI TMD Technologies, a division of Communications and Power Industries, where work continues to commercialize the microcomb, added:"Similarly, when we set the electrical current driving the laser to the appropriate value, here we are guaranteed that the microcomb will operate in our desired soliton state.

The paper, Self-emergence of robust solitons in a micro-cavity, has been published this week in collaboration with colleagues at the University of Sussex, City University of Hong Kong, the Xi'an Institute of Optics and Precision Mechanics, in China, Swinburne University of Technology in Australia, the INRS-EMT in Canada and the University of Strathclyde.

The microcomb is a core component for creating a portable and ultra-accurate time reference, which is critically needed for the current and next generation of telecommunication, network synchronization and it will reduce our dependence on the GPS. The self-emergent microcombs will be directly used in optical-fibre based calcium ion references, being pursued under Innovate UK support and the leadership of Professor Matthias Keller at the University of Sussex with CPI TMD technologies, and in a broader collaboration on Quantum Technologies including co-author Professor Roberto Morandotti at the Canadian Institut national de la recherche scientifique.

"The pursuit of next generation telecom technologies is one of the goals of our collaboration with Swinburne University and co-author Professor David Moss.".