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Exotic solitons and quantum topological edge states

New regimes for light in nanophotonics
The overarching theme of my research is using nanophotonics to access uncharted states of light. This has led us to fundamental discoveries with exciting potential in applications.

The capability to structure materials at the nanoscale opens up a plethora of possibilities to control the spatial and temporal dynamics of light. This gives us access to unexplored regimes of light propagation. For example, we recently discovered in a nanophotonic platform a new type of optical soliton, a self-forming light pulse that resembles rogue waves in the ocean. The pure-quartic soliton (PQSs), as we named it, has an outstanding potential to produce very energetic ultrashort light pulses, key in medical and industrial applications.  As another example, we are investigating nanophotonic circuits to generate and transport entangled states of light with immunity to disorder and fabrication defects, thanks to a robust property of the structure called topology.

Our recent experimental discovery of pure-quartic solitons opens up a new field of research in optics and has the potential to revolutionise the ultrafast laser realm – see our 2016 Nature Communications paper. Solitons are self-forming waves that propagate unperturbed for long distances and remain unchanged even upon collisions. They occur in many branches of physics, not only in optical systems, but also in plasma physics and atmospheric phenomena, with one of its most captivating embodiments being the rogue waves in the ocean. We discovered PQSs in a nanophotonics platform, but there is no reason to think they may not exist in other physical systems as well. One of their key features is that they support very high energies in very short pulse durations. We are currently working in this topic from two perspectives: new nanophotonic experiments that will unveil the fundamental physics governing this novel type of optical wave; and a more applied line of work aiming to develop the first PQS laser – a simple, efficient, high-power ultrafast source, could yield tremendous benefits in laser surgery of human tissue, laser tattoo removal, micromachining, and material processing in the solar cell and IT industries.

Our adventures in the fascinating field of solitons in nanophotonics platforms started way before PQSs, when we achieved the first observation of soliton compression in silicon – check out our 2014 Nature Communications paper. This had been a long-standing goal in the optics community, since it has the potential to enable the cost-effective mass production of on-chip soliton-based devices using current state of the art silicon fabrication techniques, built for the electronics industry. These soliton-based devices include mode-locked lasers, supercontinuum sources, and pulse compressors amongst other key optical processing functions. The potential benefits for the end user are therefore cheaper, greener, and more compact computing and communication devices.

In a related, but different line of research in nanophotonics, we are investigating novel states of light in topological systems. These are platforms that can provide extremely robust light propagation thanks to certain global properties of the structure called topological invariants. We recently demonstrated the first nanophotonic topological system using silicon waveguides – have a look at our Physical Review Letters. This demonstration of topologically protected guiding of light at telecommunication wavelengths in silicon highlights a path forward towards CMOS-compatible devices immune to back- scattering and environmental alterations, which could have a great impact in large scale optical integration and fault-tolerant quantum systems.

In an effort to advance towards robust quantum optical circuits we started investigating topological protection of quantum states of light and we have recently successfully demonstrated topological protection of correlated multiphoton states. One of our most important goals in this line is to achieve topological protection of entangled quantum states in a nanophotonic platform.

This research is funded by the ARC Discovery Project (DP180102234), the Professor Harry Messel Fellowship of the University of Sydney, and the ARC Centre of Excellence CUDOS (CE110001018).

 

Research capabilities

Our lab at the Sydney Nanoscience Hub is equipped with:

  • In-house developed Frequency Resolved Electrical Gating: For time- and phase-resolved ultrasensitive (sub-pJ) characterisation of ultrashort pulses of light (sub-ps).
  • Remote connection to superconducting single photon detectors in Cryostat stage: For high CAR single-photon measurements