Researchers Define New Law in Laser Physics Via Pulsation

Scientists at the University of Sydney Institute of Photonics and Optical Science have developed a new type of laser that can deliver high amounts of energy in short bursts, with potential applications in eye and heart surgery or the engineering of delicate materials.

Antoine Runge in a lab at the University of Sydney’s School of Physics. Courtesy of Louise Cooper and the University of Sydney.

“This laser has the property that as its pulse duration decreases to less than a trillionth of a second, its energy could go through the roof,” said Martijn de Sterke, the director the institute. “This makes them ideal candidates for the processing of materials that require short, powerful pulses. One application could be in corneal surgery, which relies on gently removing material from the eye. This requires strong, short light pulses that do not heat and damage the surface.”

The scientists said that to achieve their high energy laser pulses they looked into metrology and spectroscopy lasers, which use an effect known as soliton waves, which are waves of light that maintain their shape over long distances.

“The fact that soliton waves in light maintain their shape means they are excellent for a wide range of applications, including telecommunications and spectrometry,” said lead author Antoine Runge from the School of Physics. “However, while lasers producing these solitons are simple to make, they do not pack much punch. A completely different and expensive physical system is required to produce the high-energy optical pulses used in manufacturing.”

“Soliton lasers are the most simple, cost-effective, and robust way to achieve these short bursts. However, until now, conventional soliton lasers could not deliver enough energy,” said co-author Andrea Blanco-Redondo, head of Silicon Photonics at Nokia Bell Labs. “Our results have the potential to make soliton lasers useful for biomedical applications.”

In a normal soliton laser, the energy of light is inversely proportional to its pulse duration, demonstrated by the equation E ? 1/τ. If you halve the pulse time of the light, you get twice the amount of energy.

Using quartic solitons, the energy of light is inversely proportional to the third power of the pulse duration, or E ? 1/τ³. This means if your pulse time is halved, the energy it delivers in that time is multiplied by a factor of eight.

“It is this demonstration of a new law in laser physics that is most important in our research,” Runge said. “We have shown that E ? 1/τ³ and we hope this will change how lasers can be applied in the future.”

Establishing this proof of principle will enable the team to make more powerful soliton lasers.

“In this research we produced pulses that are as short as a trillionth of a second, but we have plans to get much shorter than that,” Blanco-Redondo said. “Our next goal is to produce femtosecond duration pulses, one quadrillionth of a second. This will mean ultrashort laser pulses with hundreds of kilowatts of peak power.”

“We hope this type of laser can open a new way to apply laser light when we need high peak energy but where the base material is not damaged,” de Sterke said.