Controlling solitons
Various numbers of intracavity solitons in optical microresonator © Tobias J. Kippenberg/EPFL
EPFL scientists have discovered an unanticipated way to control the number and the dynamics of soliton waves in microresonators.
Nonlinear optical microresonators are able to convert continuous wave laser light into a set of femtosecond-short pulses travelling around the resonator’s circumference. Such pulses are called “dissipative Kerr solitons”, which can propagate and maintain their shape indefinitely. Dissipative Kerr solitons could be used to boost communication data rates up to 100 TB/sec on chip-sized transmitting devices, or speed-up current spectroscopy multiple times, e.g. in spectral imaging of biological tissues or safety screenings for hazardous chemicals. Publishing in Nature Physics, EPFL scientists have now discovered a way to precisely control the dynamics and number of such solitons, thereby provide an open road for the applications.
When the solitons are extracted out of a microresonator, the output light takes the form of pulse trains whose repetition rates are determined by the size of the resonator. Smaller resonators allow us to achieve pulse trains with extremely high repetition rates reaching hundreds of gigahertz, which are of direct use for high-speed data communications and ultrahigh-resolution broadband spectroscopy applications.
The lab of Tobias J. Kippenberg at EPFL with the group of Michael Gorodetsky at Lomonosov Moscow State University has demonstrated on-demand switching between microresonator states with different number of solitons, and developed a novel approach to obtain a full control over their dynamics. The scientists demonstrate that the number of generated solitons can be deterministically controlled by the precise tuning of the driving laser’s wavelength. This provides a robust and simple way to achieve a single-soliton state in any nonlinear optical microresonator, which is a major requirement for any technological application of such devices.
The researchers also show that the stability of the solitons can be monitored with weak phase modulation of the driving laser. The measured response signal allows the prediction and prevention of the decay of the pulses, and guarantees an unperturbed long-term operation. Both techniques are shown to work in significantly different optical resonator platforms – integrated Si3N4 microrings and crystalline MgF2 resonators, and have already been successfully used by several other research groups.
The findings open the road to multiple applications of dissipative Kerr solitons by greatly facilitating the procedures of soliton generation and providing universal tools for their precise control and manipulation. The work provides a direct transfer of dissipative Kerr solitons from cutting-edge fundamental research field to real-world, applicable technology.
This work involved a collaboration of EPFL’s Institute of Physics with Lomonosov Moscow State University and the Russian Quantum Center. The study was funded by the Swiss National Science Foundation (SNSF), the Defense Advanced Research Projects Agency (DARPA), the US Air Force (USAF), the European Space Agency (ESA), the European Space Research and Technology Centre (ESTEC) and the Ministry of Education and Science of the Russian Federation project.
Reference
H. Guo, M. Karpov, E. Lucas, A. Kordts, M.H.P. Pfeiffer, V. Brasch, G. Lihachev, V. E. Lobanov, M. L. Gorodetsky, T. J. Kippenberg. Universal dynamics and deterministic switching of dissipative Kerr solitons in optical microresonators. Nature Physics 26 September 2016. DOI: 10.1038/nphys3893