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
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.
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
In a recently published article in ACS Nano, we demonstrate a SERS substrate capable of reproducible measurements, such that the relative concentration of a mixture of SERS active molecules can be determined. Surface enhanced Raman spectroscopy has become a widely used research tool for the identification of molecules, but has yet to achieve widespread use outside of academia. The dominant method for generating the required spectra is to use colloidal metallic nanoparticles, but this leads to an inherently random distribution of SERS-active sites, and thus although the signal can uniquely identify a molecule, the intensity of that signal will vary, rendering quantitative analysis impossible. We use… Read More »Reproducible SERS Substrate
In a work published recently in Optics Express we experimentally investigated the occurrence of optical dispersive shock waves (DSWs) in silica aerogel (SA). Here we studied the interplay between disorder and nonlinearity; on the other hand the determination of the conditions for the suppressions of the DSWs, is fundamental for the realization of high power nonlinear optical devices based on SA. The convection-free solid-state structure of SA gives peculiar thermal properties, such as very low heat conductivity and high melting point, making this material robust with respect to very high nonlinear regimes, a topic so far unexplored. This is at variance with most the systems presenting thermal nonlinearity, that being dyed soft-matter, exhibit boiling… Read More »Optical Shock Waves in Silica Aerogel
In a recent paper published in Optics Letter we demonstrate that a random medium can be used as a cheap and reliable wavemeter. The system is made of a small drop of alumina particles in water solution casted on a glass slide, placed at the end of a fiber coupler as in figure. When propagating through the drop, light of different wavelengths produce specific speckle patterns that can be stored for future reference. The unknown wavelength of a further beam can then be assessed using principal component analysis with a resolution up to 13 pm.
In a paper published in Nature Scientific Report we show how to couple light to subwavelenght plasmonic features using the principle of optical eigenmodes. This technique can be used also in presence of large optical aberrations and allow to selectively couple light to nanofeatures in a crowded region, with minimal crosstalk. In the picture we show a SEM picture of a typical sample (gold nanoantennas on glass) that we fabricated to test the technique.