In a paper published in Phys. Rev. Lett., we experimentally demonstrate that the distribution of phase singularities in vectorial random light fields is anisotropic. Our collaborators at AMOLF, led by Prof. Kobus Kuipers, have measured the distribution of phase singularities supported by a chaotic electromagnetic landscape, reading the surface of a photonic crystal (PhC) cavity with a SNOM. PhC chaotic resonators in silicon on insulator technology are an ideal platform to prepare a random field with repeatable and well defined characteristics. Exploiting this feature, we were able to track the deep-subwavelength phase singularities supported in the cavity. Our results demonstrate that, due to the… Read More »Spatial Distribution of Phase Singularities in Optical Random Vector Waves
We have a wide ranging portfolio of research, all focussed around the central theme of being able to have absolute control over light and its propagation. Below we have a few samples of our most recent research, and on the right is a list of all the themes we have worked on.
Our work on the “Optically Induced Metal-to-Dielectric Transition in Epsilon-Near-Zero Metamaterials” has recently appeared in Scientific Reports. In this work we designed a metamaterial with epsilon-near-zero (ENZ) response, that is tuned all-optically from a metallic to dielectric behaviour. The transition is demonstrated using an ultrafast pump and probe scheme. The study unveils both analytically and experimentally the full associated nonlinear dynamics. The full article can be found here.
In collaboration with Heriot-Watt University and Purdue University, we published a paper in Phys. Rev. Lett. demonstrating that epsilon-near-zero metamaterials (ENZ) exhibit an enhanced nonlinear response. In this study we demonstrated a six-fold enhancement of the Kerr nonlinear refractive index in proximity of the ENZ condition, in the near-infrared. The experiemtn was performed on Al-doped ZnO (AZO) thin film, and demonstrates a general behaviour of ENZ materials. The full paper can be found here.
In this work, published in Laser Photonics Review we report on the all-optical control of chaotic optical resonators based on a silicon on insulator (SOI) platform. We show that simple non-chaotic cavities can be tuned to exhibit chaotic behaviour via intense optical pumping, inducing a local change of refractive index. To this extent we have fabricated a number of devices and demonstrated experimentally and theoretically that chaos can be triggered on demand on an optical chip. We show that the degree of chaos supported by a microcavity can be controlled dynamically using light itself. We start with a square (non-chaotic) cavity obtained on SOI.… Read More »Ultrafast All-Optical Order-to-Chaos Transition in Silicon Photonic Crystal Chips
In a paper published in Physical Review Letters we demonstrate that a one-dimensional stack of achiral material can exhibit electromagnetic chirality… Artificial chirality is currently a very much-researched field both from a fundamental point of view and for its applications in molecular biology, life science, optics, crystallography and particle physics. In this context, plasmonic-based metamaterials are the natural platform of choice because their smallest constituents (meta-atoms) can be engineered to exhibit artificial chirality. This is usually achieved by breaking the spatial symmetry of the meta-atoms, structuring plasmonic materials at the nanoscale, either in 3D (akin to natural chirality) or in 2D, but never in 1D. Here… Read More »Chiral Epsilon-Near-Zero Metamaterials
In a paper published in Nature Photonics, in collaboration with researchers in KAUST (Saudi Arabia), York (UK) and Bologna (Italy) we demonstrated that chaotic resonators trap broadband light more efficiently than standard ones. The fabrication of microcavities for monochromatic light is a routine procedure in photonics. The ability to trap light efficiently for long times and in small volumes depends on how well engineered are the channels through which light is in- and out-coupled. For multimodal cavities, different wavelengths are supported by different resonant conditions and typically require specifically tuned channels. This limits the ability to transfer broadband light into a standard resonator. Here we… Read More »Enhanced energy storage in chaotic optical resonators
In a study published in Nature Physics, in collaboration with researchers from KAUST (SA), York University (UK), and AMOLF (NL), we developed an optical chip to create and control optical waves. In nature, these rare events result from the spontaneous build up of a large amount of energy, normally in a ‘quiet’ state, and can have disastrous effects. The team began research by developing new theoretical ideas to explain the formation of rare energetic natural events such as rogue waves, large surface waves that develop out of the blue in deep water and represent a potential risk for vessels and open-ocean oil platforms. Specifically we linked… Read More »Storm In A Chip
In Optical guided mode resonance filter on a flexible substrate, published in Optics Express, we present the design, fabrication and characterization of a new filtering platform, based on the principle of Guided Mode Resonance. The filters consist of plasmonic nanofeatures realised on flexible polymer substrates, and work down to the visible range. In this paper we also exhibit an example proof-of-concept application by mounting the sample directly onto the end of a collimated fibre output, as shown in the figure. This progresses research on lab-on-fibre technologies, introducing an alternative to directly fabricating structures on the end of a fibre, and rather produce fibre terminating caps which can be… Read More »Optical guided mode resonance filter on a flexible substrate
Photonic crystal fibres are an essential tool in many experiments which require their sensing or highly non-linear properties. Using our ability to fabricate flexible plasmonic structures, we have been able to functionalise the facet of a hollow core photonic crystal fibre with a spectral filter. This brings the possibility to combine Lab-on-Fibre (LoF) technologies with photonic crystal fibres, expanding the available toolkit of LoF functions. Using a flexible plasmonic membrane allows the fibre to be given a function reversibly, and without having to directly write onto the fibre’s facet itself. Crucially this allows us to realise LoF on a hollow core photonic crystal fibre, which… Read More »Nanoplasmonic Filters for Hollow Core Photonic Crystal Fibres
In collaboration with KAUST we demonstrated that a chaotic quantum resonator can be used to study the onset of superradiance, as predicted by Dicke. According to this theory, two-level atoms immersed in a common radiation field can synchronise and emit energy at a rate faster than that predicted by incoherent spontaneous emission. Experimental demonstration of this theory have so far proven elusive due to the requirement on the coupling strength of the states. Our system, based on photonic crystal resonators with controlled loss channels, mimics the dynamics of an open many-body system and permits to explore experimentally a regime with favourable coupling strength between the… Read More »Superradiance in chaotic resonators