A new home for optical solitons

January 24, 2019, Max Planck Society
Credit: Max Planck Institute of Quantum Optics

Laser physicists based at the Laboratory for Attosecond Physics run by the Max Planck Institute of Quantum Optics and the Ludwig-Maximilian University have, for the first time, generated dissipative solitons in passive, free-space resonators.

Solitons are the most stable of all waves. Under conditions that result in the dispersion of all other waveforms, a soliton will continue undisturbed on its solitary way, without changing its shape or velocity in the slightest. The self-stabilizing properties of solitons explain their immense significance to the field of laser optics, in particular for the generation of ultrashort light pulses. A team led by Dr. Ioachim Pupeza at the Laboratory of Attosecond Physics (LAP) in Munich, which is run jointly by the Max Planck Institute of Quantum Optics (MPQ) and the Ludwig-Maximilian University (LMU), has now generated optical solitons in passive free-space resonators for the first time. The technique allows one to compress laser pulses while increasing their peak power, opening up new applications for free-space enhancement cavities in the exploration of ultrafast dynamics and in precision spectroscopy.

The young engineer John Scott Russell first observed the formation of a solitary water wave in a canal in Edinburgh in 1834. He followed it on horseback, and found that it propagated at a constant velocity for miles without changing its form. He even built a water tank in his garden to investigate the phenomenon. But he could not have anticipated the subsequent significance of this 'soliton' waveform for branches of physics beyond the area of fluid dynamics. Today, optical solitons are an indispensable component of laser technology, especially in the investigation of quantum optics and ultrafast dynamics.

Physicists at the Laboratory for Attosecond Physics run by the MPQ and LMU have now, for the first time, succeeded in producing temporal optical solitons in a passive free-space resonator. To do so, they coupled 350-femtosecond infrared with a wavelength of 1035 nanometers and a repetition rate of 100 MHz, into a newly designed passive optical resonator made up of four mirrors and a thin sapphire plate.

"The passage of the electromagnetic field of the optical causes a non-linear change in the refractive index of the crystal," explains Nikolai Lilienfein, first author of the published paper. "This results in a dynamic phase shift, which fully compensates for the dispersion that occurs in the resonator, while at the same time broadening the spectrum of the pulse." Since the power losses that inevitably occur in the resonator are simultaneously compensated for by the interferometrically coupled laser source, a soliton can in principle circulate ad infinitum in the resonator. In addition, the researchers developed a highly efficient method for controlling the energy input to the cavity . In combination, these measures allowed the team to compress the duration of input pulses by almost an order of magnitude to 37 femtoseconds while enhancing their peak power by a factor of 3200.

This enhancement- technology opens up new opportunities for the generation of trains of highly precise extreme ultraviolet (XUV) attosecond pulses (an attosecond lasts for a billionth of a billionth of a second). This in turn may enable researchers to characterize the dynamics of subatomic processes – and in particular to observe the motions of electrons – in even greater detail than was possible hitherto.

"Over the past several years, we have been able to make the unique advantages of enhancement resonators available for experiments in attosecond physics. This new technique opens a path towards further significant advances in the pulse power and stability attainable with such systems, while at the same time reducing the complexity of the experimental setup," says Dr. Ioachim Pupeza, leader of the group responsible for the new work in the LAP. These improvements would also be of benefit in the context of XUV frequency-comb spectroscopy, which is central to the development of a new generation of optical clocks based on quantum transitions in atomic nuclei.

Explore further: Brief reflections from a plasma mirror

More information: N. Lilienfein et al. Temporal solitons in free-space femtosecond enhancement cavities, Nature Photonics (2019). DOI: 10.1038/s41566-018-0341-y

Related Stories

Brief reflections from a plasma mirror

December 5, 2018

When a dense sheet of electrons is accelerated to almost the speed of light, it acts as a reflective surface. Such a 'plasma mirror' can be used to manipulate light. Now an international team of physicists from the Max Planck ...

Attoseconds break into atomic interior

February 27, 2018

A newly developed laser technology has enabled physicists in the Laboratory for Attosecond Physics (jointly run by LMU Munich and the Max Planck Institute of Quantum Optics) to generate attosecond bursts of high-energy photons ...

Processes in the atomic microcosmos revealed

May 16, 2018

Physicists at Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) have successfully generated controlled electron pulses in the attosecond range. They used optical traveling waves formed by laser pulses of varying wavelengths. ...

A sense for infrared light

January 19, 2016

Laser physicists from the Max Planck Institute of Quantum Optics developed a measuring system for light waves in the near-infrared range.

Recommended for you

CMS gets first result using largest-ever LHC data sample

February 15, 2019

Just under three months after the final proton–proton collisions from the Large Hadron Collider (LHC)'s second run (Run 2), the CMS collaboration has submitted its first paper based on the full LHC dataset collected in ...

Gravitational waves will settle cosmic conundrum

February 14, 2019

Measurements of gravitational waves from approximately 50 binary neutron stars over the next decade will definitively resolve an intense debate about how quickly our universe is expanding, according to findings from an international ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.