Mode-Locked Laser Is Ultrafast, Ultrasmall

The first laser to be mode-locked using a microcavity resonator is a giant leap forward in laser technology, allowing for highly compact, fast and precise lasers.

A team led by David Moss of the University of Sydney, in collaboration with scientists from Canada, the US and Italy, used a new mode-locking method called filter-driven four-wave mixing that causes the resonator to be used as both the filter and the nonlinear element. Normally, the nonlinear interaction takes place within the optical fiber. This technique also reduces the laser's cavity length, which makes it more stable.

Integrated nonlinear ring resonator at the heart of the mode-locked laser. (Image: University of Sydney School of Physics)

"Traditional four-wave mixing schemes make the nonlinear interaction occur in the fiber, then filter the light separately using a linear Fabry-Perot filter," Moss said. "However, in our new system, we have the resonator playing these two roles, making our laser intrinsically more efficient and with a radically shorter cavity length."

The team is also the first to try using a microcavity resonator to mode-lock the laser. The resonator is a glass ring where the laser modes are generated, and it was engineered "to have ideal qualities, particularly nonlinear optical properties," Moss said.

The result was a small, high-precision laser that can pulse at fast and flexible repetition rates.

Dr. David Moss won the 2011 Australian Museum Eureka Prize for Innovation in Computer Science. (Photo: Australian Museum/247 Studios)

"Our new laser achieves extremely stable operation at unprecedentedly high repetition rates of 200 gigahertz, while maintaining very narrow linewidths, which leads to an extremely high-quality pulsed emission," he said.

Because it is stable, efficient, versatile and ultrasmall, the new laser "offers many exciting applications in a huge range of areas," Moss said, such as "computing, measuring and diagnosing diseases, and processing materials - all areas where lasers are already used. It will also open up entirely new areas such as precision optical clocks for applications in metrology, ultrahigh-speed telecommunications, microchip computing and many other areas."

Moss's laser work follows his success in computing innovation, for which he won the 2011 Australian Museum Eureka Prize for Innovation in Computer Science (See: Photonics Researchers Win Eureka Prizes). The new research was published in the April 3 issue of Nature Communications.

For more information, visit: http://sydney.edu.au