A laser that could really make waves

Physicists in Australia and the US have developed a new type of laser that can deliver high amounts of energy in very short bursts of time.

And they did it by finetuning an old idea: solitons, which were first identified in the industrial canals of England in the early 19th century.

When applied to light not water, soliton waves maintain their shape over long distances, making them useful in telecommunications, metrology and spectroscopy.

Lasers based around soliton waves are also simple and cost-effective to make but, says Antoine Runge from the University of Sydney, they don’t pack much punch. Conventional soliton lasers can’t deliver energy for manufacturing needs.

A new approach utilising shape-maintaining pulses called pure-quartic solitons, described in the journal Nature Photonics, goes some way to addressing that problem.

In a normal soliton laser, the energy of light is inversely proportional to its pulse duration, the researchers say. 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. 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,” says Runge, adding that he and his colleagues “hope this will change how lasers can be applied in the future”.

They have to date produced pulses that are as short as a trillionth of a second, but Runge says they have plans to do much better than that.

“Our next goal is to produce femtosecond duration pulses – one quadrillionth of a second. This will mean ultra-short laser pulses with hundreds of kilowatts of peak power.”

Colleague Martijn de Sterke says it’s hoped 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”.

“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,” he says.

“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.”