Author Archives: Megan

1. Light-emitting tattoo engineered for the first time

   March 15, 2021 11:17 am Leave a Comment

   Scientists from London Light and the IIT –Istituto Italiano di Tecnologia (Italian Institute of Technology) have created a temporary tattoo with light-emitting technology used in TV and smartphone screens, paving the way for a new type of “smart tattoo” with a range of potential use.

   The technology, which uses organic light-emitting diodes (OLEDs), is applied in the same way as water transfer tattoos. That is, the OLEDs are fabricated on to temporary tattoo paper and transferred to a new surface by being pressed on to it and dabbed with water.

   

   The researchers, who described the process in a new paper in the journal Advanced Electronic Materials, say it could be combined with other tattoo electronics to, for instance emit light when an athlete is dehydrated, or when we need to get out of the sun to avoid sunburn. OLEDs could be tattooed on packaging or fruit to signal when a product has passed its expiry date or will soon become inedible, or used for fashion in the form of glowing tattoos.

   Professor Franco Cacialli (co-director of London Light), senior author of the paper, said: “The tattooable OLEDs that we have demonstrated for the first time can be made at scale and very cheaply. They can be combined with other forms of tattoo electronics for a very wide range of possible uses. These could be for fashion – for instance, providing glowing tattoos and light-emitting fingernails. In sports, they could be combined with a sweat sensor to signal dehydration.

   “In healthcare they could emit light when there is a change in a patient’s condition – or, if the tattoo was turned the other way into the skin, they could potentially be combined with light-sensitive therapies to target cancer cells, for instance.

   “Our proof-of-concept study is the first step. Future challenges will include encapsulating the OLEDs as much as possible to stop them from degrading quickly through contact with air, as well as integrating the device with a battery or supercapacitor.”

   The OLED device the researchers developed is 2.3 micrometres thick in total (less than one 400^th of a millimetre) – about a third of the length of a single red blood cell. It consists of an electroluminescent polymer (a polymer that emits light when an electric field is applied) in between electrodes. An insulating layer is placed in between the electrodes and the commercial tattoo paper.

   The light-emitting polymer is 76 nanometres thick (a nanometre is a millionth of a millimetre) and was created using a technique called spin coating, where the polymer is applied to a substrate which is spun at high speed, producing an extremely thin and even layer.

   Once they had built the technology, the team applied the tattooable OLEDs, which emitted green light, on to a pane of glass, a plastic bottle, an orange, and paper packaging.

   Senior author Professor Virgilio Mattoli, researcher at Italian Institute of Technology said: “Tattoo electronics is a fast-growing field of research. At the Italian Institute of Technology we have previously pioneered electrodes that we have tattooed onto people’s skin that can be used to perform diagnostic tests such as electrocardiograms. The advantage of this technology is that it is low-cost, easy to apply and use, and washes off easily with soap and water.”

   OLEDs were first used in a flatscreen TV 20 years ago. Among the advantages of the technology are that they can be used on flexible, bendy surfaces, and that they can be made from liquid solvents. This means they are printable, providing a cheap way to create bespoke new OLED designs.

   The Full Article is available in the Advance Electronic Materials

   Image Credit: Barsotti – Italian Institute of Technology

2. Lighting Up 2021

   February 2, 2021 10:22 am Leave a Comment

   

   Bring a spark of light to 2021! Share a short video about your passion for light.

   We are seeking submissions of a 30-60s video clip to show a dimension of light that fascinates, intrigues or delights you. A streaming event to be held on 20 May 2021 with a panel of experts.

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   submit your clip here

   A number of your submissions will be selected by a panel of experts for a special screening. This will open a public debate about the shared language of light on Thursday 20th of May at 4pm GMT. 

   You can register to attend the panel event here

   Hosted by Dr Shelley James our panelists include:

   • Paule Constable – Lighting Designer
   • Mark Major – Lighting designer
   • Kailas Elmer – Publisher, Trebuchet Magazine
   • Dr James Millen – Physicist King’s College London
   • Bob Mizon OBE – Astronomer and Co-ordinator of the Commission for Dark Skies
   •  Marianne Shillingford – Colour specialist and Creative Director of Dulux,

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   Image credit: Megan Grace-Hughes Artwork:Prismatica by RAW Design in collaboration with Atomic3

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   A couple of examples are below as a starting point – but we are looking forward to seeing your creative spark! If you include music or soundscape, please can you make sure that you have permission to use it, own the copywrite or that it is royalty free

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   submit your clip here

   Submissions are now open. We will be showcasing the videos on our Instagram account over March and April.

   Deadline for last submission 23rd April 2021.

   And for more information, please contact us at london-light@kcl.ac.uk

    

   

   Many thanks to Nature Photonics for their support for this event.

    

   

3. Taking Maxwell’s equations for a spin

   9:14 am Leave a Comment

   John Clerk Maxwell developed his famous Maxwell Equations whilst working at King’s College London in the late 19^th Century. The Maxwell Equations are four equations which link the fundamental behaviour of electric and magnetic fields.

   Electromagnetic fields and waves, including light, are essential in modern technologies providing internet, mobile phones, lasers. In the quest for ever smaller and energy-efficient devices, researchers study the interaction of electromagnetic waves with nanostructures.

   As the spaces being studied are so small, often smaller than the wavelength of light or ‘sub-wavelength’, several new parameters of light waves become crucial, such as light polarisation, which define the spin of light.

   Following in Maxwell’s footsteps, a team of LCN researchers at the Physics Department, King’s College London, in collaboration with Shenzhen University in China, have developed the set of equations for spin and momentum of the electromagnetic field, which are analogous to the Maxwell’s equations.  This new set of equations allow a direct understanding of spin properties without the explicit knowledge of the electromagnetic field.

   

   In analogy to renown effects in condensed matter physics, photonic quantum spin-Hall effect and photonic skyrmions require careful description of spin properties of light waves, which is possible with Maxwell’s equations, but the derivations are lengthy and cumbersome.

   Using the newly developed equations, the team has now demonstrated the unconventional spin properties of the electromagnetic waves carrying orbital angular momentum, important for optical communications, quantum technologies, high-resolution imaging and many other fields.

   The new equations offer a shortcut for describing the unconventional spin behaviour of the electromagnetic waves, and can be applied to describe also fluid, acoustic and gravitational waves.

   Using this approach, it is very easy to see new, unexpected phenomena in the electromagnetic spin behaviour. For example, we predicted and experimentally observed dynamic behaviour of the transverse spin of guided waves arising due to spin-orbit coupling, which has completely different behaviour from the static transverse spin of evanescent plane waves.

   Professor Anatoly Zayats, Head of Photonics & Nanotechnology Group, King’s College London

   Transverse spin dynamics in structured electromagnetic guided waves is published in Proceedings of the National Academy of Sciences of the United States of America.

4. Quantum circuits with a levitated heart

   December 11, 2020 4:15 pm Leave a Comment

   A collaboration between London Light researchers and the University of Duissburg-Essen has found a way to strengthen quantum networks by levitating key components, whilst simultaneously exploring the boundaries of quantum mechanics. 

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   Do you believe in quantum physics? Quantum theory is the unchallenged description of the microscopic realm, yet seemingly has little impact on the world around us. While it is possible for photons or electrons to “be in two places at once”, known as quantum superposition, the chair you’re sitting on displays a stubborn refusal to play quantum ball. 

   
   There are good reasons why it’s hard to make big objects behave in a quantum way; quantum mechanics requires exquisite isolation to manifest its stranger behaviours. The bigger something is, the harder it is to isolate. In his lab at King’s, Dr. James Millen uses light and electrical fields to levitate microparticles in a vacuum, achieving the required isolation from the environment. Although they sound tiny, microparticles are more than a thousand times larger than the current largest quantum objects, and much larger than components used in modern electronics. 
   

   We do exploit quantum physics in technology, with companies like Google and IBM building quantum computers using tiny electrical quantum systems called qubits. The lead author on this collaborative project, Lukas Martinetz from the University of Duisburg-Essen, found a way to connect qubits and levitated microparticles, sharing their quantum behaviour with the otherwise non-quantum particles. 

   
   By working with charged microparticles, their motion can be detected and effected by nearby electrical circuitry. The team considers interfacing a charge quibit, meaning that the voltage in the circuit can be in a quantum superposition. This voltage will exert a force on the levitated microparticle, pushing it into a superposition of positions. By introducing the levitated object, the utility of the quantum circuit is greatly enhanced. Delicate quantum information can be stored in the motion of the particle, and shared between other distant qubits, building a robust quantum network. This will boost the usefulness of quantum computers, and help us build a quantum internet.
   Observing a micro-scale object in a quantum superposition would extend the reach of quantum theory into the world around us. In the future, this could be used to understand the interaction between quantum physics and gravity, one of today’s greatest scientific challenges.

   
   Quantum electromechanics with levitated nanoparticles is published in NPJ Quantum Information
   This work is supported by EPSRC New Investigator Award EP/S004777/1 and ERC Starting Grant 803277.
   

5. London Light on YouTube

   November 11, 2020 3:39 pm Leave a Comment

   The London Institute for Advanced Light Technologies now has a YouTube channel. We will be posting talks from our members, and videos of our events.

   Our first video ‘Generating colour 3D images from planar metasurfaces’ is from Dr Diane Roth from the Department of Physics at King’s College London.

   Diane is a member of the Photonics & Nanotechnology Group lead by London Light co-director Professor Anatoly Zayats.

   Her research interests are:
   •    Control of light-matter interactions with nanostructures and metamaterials.
   •    Application of plasmonic metasurfaces and structured light for optical communications, displays, security, biochemical sensing and optical trapping.
   •    Experimental verifications of fundamental physical phenomena at the nanoscale,
   •    Development and implementation of techniques for optical characterisation e.g. spectrally-resolved Fourier microscopy, complex vector beam shaping, time-resolved photoluminescence spectroscopy.

6. London Light researchers make electrical nanolasers even smaller

   October 20, 2020 4:09 pm Leave a Comment

   London Light researchers at King’s College London, in collaboration with a team at Moscow Institute of Physics and Technology have developed a concept of an electrically driven nanolaser which is not only much smaller than the other integrated lasers but even smaller than the free-space wavelength it is emitting.  The Nano-Optics group at King’s College London, led by Professor Anatoly Zayats, have previously reported on nanoscale electro-optical modulators and together these nanodevices will mark a milestone in the development of fully functional highly-integrated optoelectronic circuits for optical data communication. 

   Once incorporated into electronic computational chips, such circuitry will revolutionise on-chip data transfer, substituting ‘slow’ and lossy metallic wiring overheating the chip with broadband and energy-efficient optical network. This means that the best technology for data communication (photonics) will be merged with the best technology for data processing (electronic), leading to hybrid electronic/photonic chip architecture with superior computational power.

   Nanolasers have been at the edge of nanophotonic research of the last decade. However, the vast majority of the proposed designs utilise optical pumping schemes, requiring high-power ‘ordinary’ external lasers, which makes their practical application challenging. Electrically-pumped nanoscale counterparts met a fundamental problem when the Ti- or Cr-based low-resistance contact required to supply the electrical pumping to the optical mode simultaneously did precisely the opposite introducing unacceptable losses related to the optical absorption in the metals. The researchers have now solved this problem by proposing a novel electrical pumping scheme based on a tunnelling Schottky contact, which gets rid of highly-absorbing materials and supplies the electrical power with no loss penalties. Furthermore, the contact simultaneously confines the nanoscale optical mode in the form of surface plasmon polaritons in its vicinity – precisely in the region of most efficient amplification. Importantly, the nanolaser operates at room temperature and emits light directly into an optical waveguide, which makes it easy to integrate it into the optoelectronic circuitry. Despite the nanoscale dimensions the emitted optical power of a single nanolaser is high enough to transmit 100s of Gb/s of data, matching record-high data speeds.

   The article ‘Lasing at the nanoscale: coherent emission of surface plasmons by an electrically driven nanolaser’ was published in Nanophotonics 

   This work was funded in part by the EPSRC programme grant Reactive Plasmonics

   

   Image credit – Electrically pumped surface plasmon-polariton nanolaser – Dmitry Fedyanin

7. Future Horizons for Photonics Research 2030 and beyond report released

   September 7, 2020 12:11 pm Leave a Comment

   A ground breaking horizon scanning report on the future of photonics research 2030 and beyond has been released by the Photonics Leadership Group and the All-Party Parliamentary Group in Photonics and Quantum.  The PLG brought together 26 of the UK’s leading photonics researchers from 20 different institutions to ask “what will be the focus of photonics research a decade and more from now?”

   View the report here 

   Recognising all R&D takes place in an ever developing socio-economic environment, the report also identifies nine major challenges that photonics will have a key role in addressing. Ranging from future mobility, healthy-aging and real-time secure communications to responsive manufacturing, food production and defence; it is clear that photonics not only already makes a major contribution to society, but will be absolutely instrumental in addressing the challenges of the future.

   The report makes 7 clear recommendations to translate the identified topics into funded research balanced across all domains.  The recommendations also call on those working in vertical markets to integrate this future vision into their technology roadmaps to ensure the very best and most advance photonics is rapidly pulled through into applications for the benefit of all.

   Described by some of the UK’s leading photonics researchers as “an excellent and timely report” capturing how much  “it is an exciting time for the field”, it is hoped the highlighted topics stimulate discussion on the future directions for photonics as well as inspire the next generation of researchers.

   Co-director of London Light Anatoly Zayats said “It is very important for the photonics community to have a global view of the challenges, trends and needs of photonic science and technology in the years to come. We hope very much the document will provide the government and industry with understanding where photonics goes and its role in the future of our society.”

   John Lincoln, Chief Executive of the PLG said “It has been an incredible cathartic and inspirational exercise to take a break from all of our current challenges and look to the future and consider the huge diversity of photonics still to be discovered.”

8. Generating colour 3D images with designed reflective metasurfaces under incoherent illumination

   May 20, 2020 4:22 pm Leave a Comment

   As part of an international collaboration with Southern University of Science and Technology in Shenzhen (China), LCN researchers at King’s College London have developed a novel way of generating colour 3D images using a reflective metasurface performing through the entire visible spectral range. Metasurfaces are 2D engineered materials typically made of subwavelength elements, which provide excellent control over the shaping of optical wavefronts via the manipulation of polarisation, phase and amplitude of the light. Unlike typical metasurface-based holography techniques, the developed method does not rely on interleaved nanostructures for wavelength multiplexing or wavelength-dependent off-axis illumination. Instead, the LCN researchers used specially-designed aluminium nanostructures to achieve a high metasurface efficiency across the visible spectrum, including the three main RGB colours. A combination of specular and diffuse reflections was employed to generate images of 2D structures with 3D effects. The true perception of a 3D object through shading effects is therefore ensured by an adequate change in the brightness of the reflected light from the flat metasurface in response to variations in the illumination or observation angle. In contrast with 3D holograms, this structure performs under incoherent illumination.

   As a proof of concept, an image of a 3D cube was encoded onto the metasurface and illuminated with white light. The projected image displays shading effects changing according to the incident angle, therefore emulating the behaviour of a real 3D cube. 

   The lead author on the paper published in the journal Nano Letters, Dr Diane Roth said, “Metasurfaces are extremely versatile and have the potential to enable progress in many different areas of science, either introducing new functionalities or making existing technology smaller and lighter. The practical potential of our design is very interesting for a wide range of applications including security features for protection against counterfeiting but also artistic purposes.” More generally, the unique properties of diffuse metasurfaces could also have an impact on the development of new display technologies, flat light diffusers and integrated optical components.

   

   
   Results from this international project have been published in the American Chemical Society journal Nano Letters.

   
   Link to article in Nano Letters: 3D full-colour image projection based on reflective metasurfaces under incoherent illumination

9. What is on the Horizon for Future Photonics Research

   April 30, 2020 11:37 am Leave a Comment

   The Photonics Leadership Group have published the preliminary outputs of a recent workshop that comprised of twenty-five of the leading photonics researchers in the UK.

   The academics were asked ‘What is on the Horizon for Future Photonics Research?’ to generate a picture of where photonics research will be focused in ten years time. The raw output of that workshop is captured in the summary of seventy topics identified as offering significant potential for future investigation (shown below).

   The detailed outputs will be published in a full report in the summer of 2020.

   You can read more on the Photonics Leadership Group webpage.

   

   Click to see full-sized image

    

    

10. Nobel laureate tells how to beat his own award-winning imaging technique

    February 20, 2020 10:28 am Leave a Comment

    In the 1990s an optical imaging technique emerged that overturned the “diffraction limit”, which for over a century had defined the maximum achievable resolution an optical microscope could achieve at around half the wavelength of the illuminating light. At King’s College London’s Wheatstone Lecture 2020, attendees heard from Stefan Hell, the Nobel laureate who had developed the technique – stimulated emission depletion microscopy (STED). In his talk he described a new kid on the block in the world of optical imaging techniques that can beat the resolution of STED by a further factor of 10.

    Hell began his talk with an overview of his STED technique and two others developed in the 2000s – photo-activated localization microscopy (PALM) and stochastic optical reconstruction microscopy (STORM) – that together led to the award of the 2014 Nobel Prize for Chemistry to Eric Betzig, Stefan W. Hell and William E. Moerner “for the development of super-resolved fluorescence microscopy.”

    “I’m still struggling with this chemistry thing,” smiled Hell “I don’t know much about chemistry.” Despite the modesty of his claim, as his talk pointed out all these super-resolution techniques hinge on the use of fluorescing molecules that stain the sample being imaged. The chemistry becomes important for choosing the right molecules that will fluoresce with the right behaviour – emitting photons and “bleaching” or ceasing to emit them when flooded with light, only in ways that allow the techniques to work. Nonetheless he was true to his word that there wouldn’t be too much chemistry in the talk, giving instead a tour de force of the physics behind these techniques.

    Both STED and PALM/STORM illuminate a diffraction-limited region to excite the molecules there to fluoresce. However, STED uses an additional, for example, doughnut-shaped beam to deplete emissions from part of this region, while PALM and STORM use the stochastic nature of the molecules’ fluorescence and bleaching to build up a picture with a resolution that beats the diffraction limit. Both techniques should be capable of resolution at the molecular level but as Hell pointed out, in practice they are limited to a resolution of ten times this at around 20 nm. This is still ten times better than diffraction-limited optical microscopy can achieve, but he was keen to resolve molecular level detail, which is what is achieved by his group’s new technique “MINFLUX”.

    Hell described the Achilles heel of the previous super-resolution techniques – the sheer number of photons needed. In contrast MINFLUX operates by the absence of photons emitted. It tracks fluorescing molecules with a doughnut shaped illuminating beam where fluorescence is suppressed in the centre, and uses the known mathematical description of how that fluorescence changes from the centre of the hole in the beam to pinpoint the molecule from what photons have been emitted. In an ideal world tracking the molecule with it dead centre of the beam would involve no fluorescence at all. This not only liberates the achieved resolution from a performance limited by the number of photons involved but means that images can be collected much faster – something biologists love. He showed a movie of a protein moving around in an e coli cell where the technique tracked 8000 protein localizations a second.

    The Wheatstone Lectures are an annual event at King’s College London that attract lay public and academics alike. The excitement of one University College London student pursuing a Masters on super-resolution techniques was infectious as he waited to hear the man who had won a Nobel Prize for work in this field describe the state of the art. The lectures commemorate the life and work of one of the college’s alumni Charles Wheatstone (1802-1875), a scientist and prolific inventor whose legacy includes the symphonium, the stereoscope and work on establishing the telegraph system and the Wheatstone Bridge.

    

    Professor Stefan Hell – Delivering the Wheatstone Lecture 2020

     

    Photo credit: King’s College London Department of Physics

    Words: Dr Anna Demming