We often take it for granted, but every time we send an email, stream videos or use a social network, we make use of a complex network infrastructure of fiber-optic cables connecting remote parts of our planet. Fiber-optic communication systems rely on a technology called wavelength division multiplexing, whereby hundreds of lasers of different frequencies are used to cover the bandwidth available in the fiber link. All these lasers can in principle be replaced by a single light source known as microresonator frequency comb — a chip-scale device that generates multiple evenly-spaced frequencies when pumped by a single-frequency laser. Replacing multiple lasers with a single one is an extremely promising prospect for decreasing energy consumption in data communications while enabling extremely fast data transmission.
However, one practical concern when dealing with a single-laser source for wavelength division multiplexing is the amount of power that can be obtained per channel. A key outstanding issue with microresonator frequency combs is that they display relatively low power conversion efficiency, meaning that only a fraction of the input power of the laser is successfully transferred to the new frequency components. The overall objective of DarkComb is to investigate a novel microresonator comb source called “dark soliton”, which displays unusually high-power conversion efficiency, but has been very little investigated by the research community. This aim requires: (1) to understand the fundamental complex nonlinear interactions of dark solitons in optical microresonators, (2) to develop a suitable arrangement of ultra-low-loss microresonators for generating dark solitons with a performance compatible with fiber communication systems and (3) to realize system-level experiments demonstrating unprecedented communication speeds. If successful, the DarkComb project will mark the start of a new, practical, high-performance and compact technology platform that will enable the next generation of optical communication systems.
