Physicists based at Ludwig Maximilian University (LMU) and the Max Planck Institute for Quantum Optics have generated temporal, dissipative, optical solitons in passive, free-space resonators. The advance could open up new applications for free-space enhancement cavities in precision spectroscopy and for the exploration of ultrafast dynamics. Development of new enhancement cavities at the Laboratory for Attosecond Physics. Courtesy of Thorsten Naeser. The team led by Ferenc Krausz generated a 37-fs sech²-shaped pulse with a peak-power enhancement of 3200, exhibiting low-frequency intensity noise suppression. Their discovery could help scientists further compress laser pulses while further increasing their peak power. Due to their self-stabilizing properties, optical solitons are seen as an indispensable component of laser technology, said the researchers. Under conditions in which all other waveforms are dispersed, a soliton will continue undisturbed on its solitary way, without changing its shape or velocity. Solitons have been used for the generation of ultrashort pulses and frequency combs in active and passive laser architectures. According to the team, the power scalability unique to free-space cavities, the combination of peak-power enhancement and temporal compression, and the cavity-soliton-specific noise filtering indicate the potential of optical solitons for applications including spatiotemporal filtering, compression of ultrashort pulses, and cavity-enhanced nonlinear frequency conversion. The research was published in Nature Photonics (https://doi.org/10.1038/s41566-018-0341-y).