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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.

Anti-reflection coatings for epsilon-near-zero materials

In this article we design and fabricate an anti-reflection layer for a multilayer epsilon-near-zero metamaterials. The layer is designed using a Multi-Objective-Grey-Wolf-Optimizer (MOGWO), using the same constituent materials of the ENZ stack. The anti-reflection layer yields a transmission enhancement of 20% over a 150 nm range and reflection minimization of 50% over a 200 nm range, respect to the uncoated sample.

Two-tier manipulation of holographic information

In this paper, published in Optics Express, we design and experimentally demonstrate the two-tier manipulation of optical information using holographic metasurfaces. Our devices encodes different information that can be retrieved if two keys are simultaneously used. Here, one key is the wavelength used to probe the holographic metasurfaces. The other key is the medium in which the metasurface is held. Specifically, one image is obtained for visible light at 705nm and air and a different, uncorrelated image is obtained for a wavelength of 750nm in water. The key element that enables our technology is the use of resonant meta-atoms (the unit cell of the  metasurface)… Read More »Two-tier manipulation of holographic information

ERC PoC – Holophrase

We are happy to share the news that the group has been awarded an ERC Proof of Concept grant, to develop an integrated on-chip pH sensor. HolopHrase is based on the ERC consolidator grant AMPHIBIANS, which introduces the metasurfaces technology in microfluidic environments. With HolopHrase, we will develop a flexible solution for the real time, label free, quantitative optical imaging readout of the pH level of a liquid solution. Our approach brings together the ease of access, simplicity, and cost of bulkier solutions, with the accuracy and level of integration of the most sophisticated sensors. Our device creates a holographic image that changes in real… Read More »ERC PoC – Holophrase

All-optical manipulation of photonic membranes

In this paper, we demonstrate the all-optical manipulation of polymeric membranes in microfluidic environments. The membranes are decorated with handles for their use in holographic optical tweezers systems. Our results show that due to their form factor the membranes present a substantial increase in their mechanical stability, respect to micrometric dielectric particles. This intrinsic superior stability is expected to improve profoundly a wide range of bio-photonic applications that rely on the optical manipulation of micrometric objects.    

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