Research

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.

Perfect secrecy cryptography in photonic chips

We are very happy to share our new paper where we demonstrate that it is possible to create a perfect secrecy cryptographic protocol in classical channels. The system uses time varying integrated chips based on silicon on insulator technology and implements a working version of the One Time Pad protocol. The work was the result of the collaboration between our group, King Abdullah University of Science and Technology (KAUST) and the Center for Unconventional Processes of Sciences (CUP Sciences). You can access here the press release from the University of St Andrews.  

The Nonlinear Optical Memory Effect

Light propagating in random media produces characteristic speckle patterns, which remain correlated for small perturbations of the parameters of the incoming beam, including e.g. its angle and position. This behaviour is known as memory effect. In a paper published in Optics Letters, fruit of the collaboration of our group with Dr Tom Vettenburg (University of Dundee) and Prof. Claudio Conti (CNR, Italy), we generalise the memory effect to the case of light propagating in random nonlinear media. In particular, in a series of pump-probe experiments, we quantify the nonlinear memory effect produced by the opto-thermal response of silica aerogel. In this work, the memory effect… Read More »The Nonlinear Optical Memory Effect

Flexible Patches for mm-Wave Holography

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In a paper, published in Applied Physics Letters, we present a flexible holographic metasurface operating in the mm-wave range. The implementation of this metasurface is a three-layer structure using c-rings to encode the hologram and is implemented in both rigid and flexible designs. Furthermore, we present simulations and experimental results of the resultant holographic images. This work is of practical relevance for retrofitting existing mm-wave equipment for applications related to antennas (e.g. for 5G) and electromagnetic shielding.

Perturbation of Transmission Matrices in Nonlinear Random Media

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In this paper, published in Annalen der Physik, we present the direct measurement of the nonlinear transmission matrix of complex materials, exploiting the strong optothermal nonlinearity of scattering silica aerogel. It is shown that the dephasing effects due to nonlinearity are both controllable and reversible, opening the road to applications based on the nonlinear response of random media  

Patterning Multicolor Hybrid Perovskite Films via Top-Down Lithography

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In this paper, published in ACS Nano, we present a platform for lithographically defining micron-sized features with flat tops in lead-haldide perovskites. Our method uses standard resists at low temperatures. Furthermore, we expand this platform to produce arrays of multi-colour pixels for commercial perovskite LED display applications.

Conformable optical coatings with epsilon near zero response

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In this paper, published in APL Photonics, we design and experimentally demonstrate an optical free-standing and low-loss epsilon-near-zero (ENZ) metamaterial which shows a vanishing effective permittivity at the visible range. We fabricate the flexible ENZ membrane using the sacrificial layer-assisted method by stacking polymer (SU-8) and silver nano-layers. The obtained membranes do not show any sign of degradation even after several thousand bending cycles (BCs). Additionally, we demonstrate that our ENZ material can conform to targets with a radius of curvature of a few microns. This material permits to coat any substrate or device with a tailored made “photonic skin”, decoupling the fabrication requirements from… Read More »Conformable optical coatings with epsilon near zero response

Integration of sub-micron semiconductor lasers in living cells

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In a paper published in Nature Communications, we report on the integration of sub-micron semiconductor lasers in living cells. In this work, fruit of the collaboration with Malte Gather and his group at the University of St Andrews, we demonstrate that lasers with dimensions much smaller than that of many cell nuclei can be used to tag individual cells and sense their environment. This research paves the way for a new bio-photonics platform that will provide new insight into cell biology, including research in immune cells, neutrons and cancer cells. A. H. Fikouras, M. Schubert, M. Karl, J. D. Kumar, S. J. Powis, A. Di… Read More »Integration of sub-micron semiconductor lasers in living cells

Photonic trimming of quantum emitters via direct fabrication of metallic nanofeatures

In a paper published in APL Photonics we demonstrate the control of the emission of a GaAs quantum dot (QD) embedded in a GaAs/AlGaAs nanowire (NW) by the post-fabrication of a plasmonic grating on its surface. We fabricated a sub-wavelength Pt grating directly on the NW surface, via electron beam induced deposition, to enhance the emission efficiency of QD for the polarization parallel to the NW of 45%, with a 17% reduction in the photon lifetime. These findings and EBID approach offer great opportunities for the development of nanopatterned QD emitters and new hybrid nanophotonic platforms for efficient single photon sources.

Flexible Holographic Metasurface with Surface Topology Dependent Functionality

In a paper published in ACS photonics, we present a flexible holographic metasurface with surface topology dependent functionality. We demonstrate that the phase contribution of the non-flat metasurface shape determines the symmetry properties of the far field holographic image. Here we also describe a framework to increase the sensitivity of the holographic image to the exact metasurface topology.   This work is of practical relevance for security printing technologies, as well as surface polarization and surface topology sensors.

Persistence and Lifelong Fidelity of Phase Singularities in Random Waves

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In this paper we show that Photonic Crystal chaotic resonators are a convenient platform to address the dynamic of optical phase singularities in random light landscapes. In particular, our collaborators at the Kavli Institute of Nanoscience of the Delft University of Technology have measured the fidelity and persistence of couples of singularities, as the wavelength is tuned within the bandgap of the resonator. The results unveil the non trivial statistical properties of singularities respect to their faithfulness.