RPLAS exhibit demos at Knowledge Transfer Network event

Representatives from King’s College London travelled to Birmingham this week to exhibit demos at SET 2019 Metamaterials.

Showcasing Emerging Technology is a series of events organised by the Knowledge Transfer Network (KTN) where groundbreaking research can be shared with industry.  The KTN, which is part of Innovate UK, helps businesses get the best out of creativity, ideas and the latest discoveries, to strengthen the UK economy and improve people’s lives.

The RPLAS team were exhibiting their Ultrasensitive Metamaterial Sensor for the Optical Detection of Gases. This technology is based on optical metamaterials
comprised of subwavelength metallic nanorods. The sensor is made up of an LED light source and a photodetector. When hydrogen is present there is a change in the reactive index of the palladium nanorods in the metamaterial which can be plotted and detected.

The team believes that this set up could be miniaturised and reproduced relatively cheaply and could be useful to the chemical industry. Look out for the RPLAS team at other events over the coming months.

KTN

 

 

 

 

 

 

 

 

 

 

 

 

New open access journal Advanced Photonics

Professor Anatoly Zayats (RPLAS PI) is the co-editor-in-chief of a new journal that is published by SPIE and Chinese Laser Press. Advanced Photonics is a collaborative, open-access journal, featuring the most impactful fundamental and applied research across optics and photonics technologies.

Advanced Photonics, designed to address a growing demand within the photonics community to publish and share significant, innovative research results as rapidly, accurately, and accessibly as possible, will highlight scientific and technological discoveries as well as news and commentaries by leading experts and visionaries in the field.

Advanced Photonics will also incorporate a personal approach to science, with interviews and the personal views of authors and how their new ideas emerged. Speaking about this approach, the editors said ‘We hope this will make an exciting mixture of scientific and general material for our readers’

Advanced Photonics Cover Issue 1

New hyperbolic metamaterial fabricated by RPLAS researchers.

A new type of hyperbolic metamaterial has been developed by Reactive Plasmonics at King’s College London (KCL) allowing scientists to have greater flexibility of manipulating light-matter interactions at the nanoscale.

Hyperbolic Metamaterials are artificial subwavelength-structured media that exhibit unusual optical properties and display indefinite dispersionThey are usually fabricated as metal nanorod assemblies or multilayers on substrates. Researchers in the Department of Physics at KCL have now developed a version of a hyperbolical metamaterial in colloidal form. Published in Laser & Photonics Reviews these hyperbolic metaparticles are dispersed in a solution and may find applications in plasmonenhanced spectroscopy, nanolasers, design of nonlinear phenomena, photothermal conversions, and hotelectron generation.

 

Dr Pan Wang was able to make hyperbolic metaparticles using a wet chemistry method coating nano-objects with alternating silica and gold multishells. The highly anisotropic silica/gold multishells display a hyperbolic dispersion and allow the engineering of refractive index on demand, providing great flexibility in the design of the optical properties of the metaparticles. 

 

The concept of creating hyperbolic metaparticles by coating nano-objects with curved metal-dielectric multilayers.

 

 

 

 

 

Compared with traditional bulk hyperbolic metamaterials, metaparticles in the colloidal form show many interesting advantages such as high flexibility in use (e.g., can be dispersed in a solvent, self-assembled on a surface, or embedded in a bulk matrix) and easy excitation of hyperbolic modes by direct illumination, making them promising for many applications. For example, they can be used as optical antennas for the enhancement of spontaneous emission rate of emitters by directly dispersing them into an active solution or spreading them on an active surface. It is also possible to make metaparticles active by incorporating optical gain, such as dye molecules or quantum dots, directly into the silica shells, which is attractive for developing ultra-small nanolasers. In addition, single metaparticles can work as building blocks for the creation of complex hyperbolic structures via self-assembly, which are difficult to realize using existing fabrication methods.

RPLAS researchers participate in the Photonics Innovation Village 2018

The Reactive Plasmonics team from King’s College London took a trip under the channel to France this week to attend SPIE Photonics Europe 2018.

As well as participating in the main conference, the team took part in the 2018 Photonics Innovation Village which aimed to showcase the research and innovative products from universities, nonprofits, and research centres.  It enabled the researchers to share their latest findings to industry innovators and other photonics visionaries.

One of the items on show was an ultrasensitive metamaterial sensor for the optical detection of gases. The sensor is made up of an LED light source and a photodetector. When hydrogen is present there is a change in the reactive index of the palladium nanorods in the metamaterial which can be plotted and detected.

The team believes that this set up could be miniaturised and reproduced relatively cheaply and could be useful to the chemical industry.

RPLAS scientist takes her research to Parliament


 RPLAS researcher Margoth Cordova Castro is a PhD student at King’s College London.


Margoth attended Parliment on the 12th March to present her physics research to a range of politicians as part of STEM for BRITAIN 2018. Her poster was shortlisted from hundreds of applicants to appear in Parliament. (You can view the poster at the bottom of the page)

On presenting her research in Parliament, she said, “It’s an honor be part of this multidisciplinary event and meet brilliant young researchers and know about the very interesting research all around UK. Sharing with politicians some of the results we achieved with our everyday hard work with the same motivation: push the boundaries of knowledge and try to bring new ideas and solutions to the real problems we are currently facing.’

Stephen Metcalfe MP, Chairman of the Parliamentary and Scientific Committee, said: “This annual competition is an important date in the parliamentary calendar because it gives MPs an opportunity to speak to a wide range of the country’s best young researchers.

“These early career engineers, mathematicians and scientists are the architects of our future and STEM for BRITAIN is politicians’ best opportunity to meet them and understand their work.”

The Parliamentary and Scientific Committee runs the event in collaboration with the Royal Academy of Engineering, the Royal Society of Chemistry, the Institute of Physics, the Royal Society of Biology, The Physiological Society and the Council for the Mathematical Sciences, with financial support from the Clay Mathematics Institute, Research Councils UK, Warwick Manufacturing Group, Society of Chemical Industry, the Nutrition Society, Institute of Biomedical Science and the Heilbronn Institute for Mathematical Research.

11111printsTEMargoth

 

New journal in Advanced Photonics to be published in 2019

RPLAS Principal Investigator, Anatoly Zayats is to become Co-Editor-in-Chief of a new journal that will be published next year.

Advanced Photonics will be published by SPIE, the international society for optics and photonics and Chinese Laser Press. It is being sponsored by Shanghai Institute of Optics and Fine Mechanics and the Chinese Optical Society.

This will be a highly selective, open access, international journal, publishing innovative fundamental and applied research in optics, photonics, and related fields.  Advanced Photonics will feature top-quality original papers, letters, and review articles, reflecting significant advances and breakthroughs in theoretical and experimental research, and promising novel applications. The journal will include news and commentaries covering scientific and technological discoveries, breakthroughs, and achievements.

Anatoly Zayats said : “We aim to make Advanced Photonics a trusted source of groundbreaking research in optics and optical technologies. With the benefits provided by open access, we hope the journal will be on a reading list of all researchers interested in new trends in photonic sciences.”

More details can be found here

 

 

 

New nanomaterial could enable new types of chemical processes in pharma, materials and chemical industries

Reactive Plasmonics researchers at King’s College London have engineered a new nanoscale device which creates a controlled stream of ‘hot electrons’ – high energy electrons which allow unusual chemical reactions to take place. This could open up new research avenues for pharma, chemicals and materials industries.

The research, published in Nature Nanotechnology, describes how a metamaterial – a material with properties not found in nature – can be constructed which uses quantum effects to turn electrons flowing through a circuit into hot electrons and light, in a highly controlled manner. This has a wide variety of novel applications in opto-electronics, sensing, and chemistry.

The device takes advantage of a quantum effect called electron tunnelling to produce streams of particles which can have important applications, when properly controlled.

A voltage is applied across the device, causing a flow of electrons from one material (eutectic gallium indium) to another (gold nanorods).  These are separated by an air gap, which would usually stop the electron flow. But when the air gap is less than a nanometer, quantum mechanical rules apply, which allow the electrons to ‘tunnel’ through.  This tunnelling produces two useful effects.

Firstly most of the tunnelling electrons arrive in the gold nanorod tips in the form of ‘hot electrons’. Hot electrons are of great interest to chemical industries, since their high energies allow chemical reactions to occur between molecules which would not normally react with each other.

Secondly, a small proportion of the tunnelling electrons excite other particles (called plasmons) in the metamaterial. These excitations emit light, the wavelength of which is directly related to the applied voltage. Usually this conversion is very inefficient, but the King’s metamaterial uses array gold nanorods providing one hundred billion tunnel junctions to improve the electron-to-plasmon conversion, making the emitted light visible to the naked eye.

The creation of hot elections is very useful to a wide range of industries that are interested in creating new chemicals that do not occur under normal conditions. For example they could be used to synthesise new molecules in pharma and chemical industries which require high energies. It can work as a lab-on-a-chip device for developing and understanding new chemical reactions where precise stimulation and monitoring are paramount.

To demonstrate the device, the team performed oxidisation and reduction reactions involving oxygen and hydrogen molecules.  Hot electrons have previously been produced using light. But this method leads to a broad distribution of energy across the excited electrons. The new tunnelling technique creates hot electrons with consistent and controllable energy levels, allowing for very precise control of reactions. This new material therefore allows highly tunable production of hot electrons and so can be used to control chemical reactions with much greater precision.

The tunnel junctions (the air gap) in the material are very sensitive to changes. For example the new products from a chemical reaction in the junctions will dramatically affect the tunnelling properties, changing the flow of electrons, so its presence can be detected by monitoring the change in current or light. This means the materials can also be used to closely monitor the reactions it is enabling.

Similar principles can be applied for monitoring the presence of gasses. The King’s material was designed to be sensitive to hydrogen and oxygen, two chemicals where there is a great need for sensitive monitoring, and was shown to reliably detect these chemicals. Detecting hydrogen leaks is important in the production of fuel cells, and monitoring the presence of oxygen is vital in a wide variety of controlled chemical reactions, such as in the manufacture of drugs.

The material can be modified to be sensitive to different molecules, making it viable as a highly sensitive, cheap, and easy to use sensor which provides visual feedback when a molecule is detected.  A further benefit of the material is in small scale electronics. Since light is generated by applying a voltage along the nanorod which is only ten nanometers thick, it can be used to optically transmit information (1s and 0s produced by rapidly turning the light on and off) between or within microchips.

This is usually done with semiconductor lasers, but as electronics get smaller the semiconductor devices become too bulky. The King’s metamaterial allows the optical signals to be produced with a much smaller device, bringing advantages to chip manufacturers and facilitating the development of ever faster electronics.

Dr Pan Wang, lead author of the paper, says: “This one tiny device offers several amazing applications: plasmon excitation, light generation, and chemical reaction activation. And all this is achieved by a small, easy to produce material which only requires a small voltage to function.”

RPLAS Principal Investigator Professor Anatoly Zayats concludes: “When we began these studies we expected to generate some weak light which we thought should be enough for various nanophotonic applications on a chip. But as sometimes happens in the research, the applications are much richer. We believe the potential of the approach for designing chemical reactions stimulated with hot electrons and monitoring chemical processes for drug and materials discovery is huge.”

 

Scientists develop ultra fast method of changing fundamental property of light

Researchers from the Reactive Plasmonics team at King’s College London have developed a new method for rapidly changing the polarisation of light, one of its fundamental properties. The research, published in Nature Photonics, could lead to much faster data transfer and advance research into nano-materials.

A light wave undulates in different ways – known as its polarisation. The polarisation of light is changed by the material it passes through, so we can use it to learn about unseen nano-scale worlds such as drug chemistry and quantum electronics. Switching polarisation is also used to transfer digital information along fibre optic cables.

The electronic methods currently used to control the light polarisation in such applications is reaching its physical speed limit.  Researchers at King’s have overcome this problem, allowing polarisation to be switched at timescales of less than a millionth of a millionth of a second – hundreds of times faster than current electronic methods.

This will allow us to ‘see’ very fast nano-scale processes such as chemical reactions for the first time, by illuminating them with rapidly changing light. This helps us to understand the difference in formation of nasty chemicals and life-saving drugs, and allows us to study new materials that will bring about the next technological revolutions.  This will also represent a major advance in data transfer speeds. By rapidly changing the polarisation of light – to represent a one or a zero – data can be passed along fibre optic cables and into your living room more rapidly. This will help meet growing data sharing demands driven by streaming and cloud services.

The team designed nano-structured materials that can control light polarisation using light itself – a technique known as ‘all-optical polarisation control’.  These nano-structures are known as metamaterials: materials with optical properties not available in nature. These thin, lightweight materials are constructed from elements smaller than a thousandth of a millimetre in order to create exotic optical effects.

In this case, the metamaterial is constructed of gold nano-particles. A high intensity light pulse is fired into the metamaterial, injecting energy into electrons in gold particles, which in turn changes the refractive index of the material.

A second pulse is fired at the metamaterial at the same time. As this pulse passes through the material, the change in refractive index changes its polarisation. This all happens instantaneously, allowing polarisation to be changed trillions of times per second.  By simply shining two beams of light through the material, one beam is able to control the polarisation of the other at ultrafast speed.

The effect can be observed even with one beam. In this case, the polarisation of the light transmitted through the metamaterial changes with the intensity. It is like polaroid sunglasses which adjust themselves to remove glare whenever it is too much sunlight.

Luke Nicholls, the PhD student who carried out these experiments, said, “With everybody using more and more data, streaming videos, music and sharing pictures, we are fast approaching a point where the current internet infrastructure will not be able to cope. All-optical control provides an answer to this looming problem and hopefully sees an end to staring at the infuriating buffer wheel.”

 This research also has potential beyond how many box sets we can download. Control of light at such short time scales could also feed into quantum information processing, where controlling the polarisation of light is integral for building successful quantum computing devices.

 

Reactive Plasmonic’s PI Anatoly Zayats of King’s College concludes: “This effect opens up many opportunities for new applications which can directly impact everyday life. The faster you can control light polarisation, the faster you can use light to transmit data and make measurements.”

 

Metamaterial_Illustration-01This groundbreaking research has been featured in the following publications

New Electronics

Drug Discovery Today

Electronics Weekly

Photonics

Electro Optics

Engineer

 

Images of 3D objects appear on nanostructured surface

Professor Anatoly Zayat’s and Dr Alex Minovich from King’s College London have developed new 2D nano-surfaces which appear as realistic 3D objects – including shading and shadows – using cutting edge nano-engineering. The research was carried out  alongside Rheinische Friedrich-Wilhelms-Universität Bonn, and is published in the American Chemical Society journal Nano Letters.

When light hits an object, the colour, texture, and shape affect how light is absorbed and reflected, allowing you to make out the object in front of you. By altering the surface to change how light is reflected, it is possible to manipulate how it appears.

The researchers developed layered materials, incorporating precisely designed nano-features smaller than the wavelength of light – called metasurfaces. This allowed them to control how light is reflected in highly precise ways, so that a 2D surface reflects light just as a 3D object would.

Borrowing a technique from 3D graphics called Normal Mapping, researchers encoded shadow effects into the image, creating 3D images more realistic than holograms or 3D cinema. As a proof of concept, the researchers fabricated a flat metasurface imitating lighting and shading effects of a 3D cube.

Capture

The technique could have huge implications for the optical industries, including in TV screens and photography.

Professor Anatoly Zayats of King’s College says: “Metasurfaces are amazing. They open up unprecedented freedom in directing and manipulating light. One might ultimately imagine a TV screen which appears exactly the same as you move around it, or a new movement of 3D art”.

The ability to control light could bring new functionality to small camera lenses. A flat surface can be made to appear optically convex by designing appropriate metasurface properties. Future generations of smartphone cameras could use the tiny flat metasurfaces which mimic the properties of sophisticated curved camera lenses, allowing much greater control of angle and depth field.

The wafer thin materials could also replace heavy optical lenses in applications such as satellites, where weight and size have a big impact on efficiency.

More immediately, the novel nano-materials could already be used to create unique complex 3D images for security and anti-counterfeiting applications, as well as for new measurement applications requiring precise control of light.