Record-shattering ultrashort laser pulses created, reach 100 MW peak power

Researchers at ETH Zurich have developed a laser oscillator that produces the most powerful ultra-short laser pulses ever.

The pulses from the laser last for less than 10 ⁻¹² seconds. However, on average, they carry 550 watts of power, with peak power output reaching 100 megawatts — this is more than enough to power hundreds of thousands of vacuum cleaners together for a short duration.

“They surpass the previous maximum by more than 50 percent. This is, to the best of our knowledge, the highest average power and highest pulse energy ever achieved for any modelocked oscillator,” the researchers note.

These super-intense and short-lived pulses could be used for performing complex tasks, such as material processing, surgical treatments, and precision measurements. Also, they could lead to the development of more accurate atomic clocks.

Mirrors create strong laser pulses

Devices that generate and shoot continuous laser beams are more common because it’s easier to emit light steadily while using a stable energy source and feedback system.

However, producing short laser pulses is a much more complex process. This is because it requires advanced techniques like Q-switching or mode-locking to release energy in bursts, demanding specialized equipment and precise control.

During their study, the researchers used a type of laser oscillator called a short-pulsed disk laser that incorporates the above-mentioned techniques.

The first task was to amplify the light inside this laser without making it unstable. For this, they used a special arrangement of mirrors. These mirrors made the light pass through the disk multiple times before it could leave the laser through another mirror.

Once the light was amplified, the next challenge was to turn it into powerful and short laser pulses. For this purpose, they used a special mirror called SESAM (Semiconductor Saturable Absorber Mirror). It was originally developed 30 years ago by Ursula Keller, one of the study authors and a physics professor at ETH Zurich.

Conventional lasers use amplifiers to create pulses, but this process is inefficient, produces noise, and leads to unstable power output . With SESAM, the researchers overcame all these challenges and efficiently turned the laser light into powerful pulses.

“When it finally worked and we watched how the laser created pulses – that was really cool,” Moritz Seidel, lead researcher and a PhD student at ETH Zurich, said .

A new way of producing pulses

The current study solves many challenges associated with producing powerful ultra-short laser pulses.

For instance, “pulses with powers comparable to the ones we have now achieved could, up to now, only be achieved by sending weaker laser pulses through several separate amplifiers outside the laser,” Seidel said.

The findings of the study suggest that laser oscillators combined with semiconductor material-based mirrors like SESAM, can work as a great alternative to amplifiers. They offer controlled, precise, and powerful laser pulse production .

Ultra-short laser pulses can be useful for a variety of applications , ranging from LASIK eye surgeries to optical quantum computing systems and creating intricate microstructures in metals.

Excited with the results of this research, “we now also expect to be able to shorten these pulses very efficiently to the regime of a few cycles, which is very important for creating attosecond (10 ⁻¹⁸ seconds) pulses,” Keller concluded.

The study is published in the journal Optica .