Author Archives: Megan

1. 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.
   

2. 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.

3. 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

4. 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.”

5. 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

6. 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

    

    

7. 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

    

    

    

    

    

8. Nader Engheta – 2019 OSA Annual Lecture – Imperial College London

   December 2, 2019 8:57 am Leave a Comment

   Imperial College Optics Society is proud to announce that the 2019 OSA Annual Lecture will be given by Prof. Nader Engheta on Metaphotonics. 

   The event, free of charge, will take place in the South Kensington Campus of Imperial College, Huxley Building, in Lecture Theatre 308, on Friday 13th December 16:00-17:00, and will be followed by drinks and snacks in the Level 8 common room of the Blackett Laboratory, where attendees will have a chance to discuss with Prof. Engheta and other researchers present.

   Abstract:

   Materials are often used to manipulate waves. Metamaterials have provided far-reaching possibilities in achieving “extremes” in such wave-matter interaction. Various exciting functionalities have been achieved in exploiting metamaterials and metasurfaces in nanophotonics and nano-optics.

   We have been exploring how extreme metamaterials can give us new platforms in metaphotonics for exploiting waves to do certain useful functions for us. Several scenarios are being investigated in my group. As one scenario, we have been developing metastructure platforms that can perform analog computation such as solving integral and differential equations and inverting matrices with waves as waves interact with them. Such “metamaterial machines” can function as wave-based analog computing machines, suitable for micro- and nanoscale integration. Another scenario deals with 4-dimensional metamaterials, in which temporal variation of material parameters is added to the tools of spatial inhomogeneities for manipulating light-matter interaction. The third category for metaphotonics is the concept of near-zero-index structures and associated photonic doping that exhibit unique features in light-matter interaction, opening doors to exciting new wave-based and quantum optical features.

   In this talk, I will present some of our ongoing work on extreme material platforms for metaphotonics, and will forecast possible future research directions in these paradigms.

   Ticket are available here –

   Biography:

   Nader Engheta is the H. Nedwill Ramsey Professor at the University of Pennsylvania in Philadelphia, with affiliations in the Departments of Electrical and Systems Engineering, Bioengineering, Materials Science and Engineering, and Physics and Astronomy. He received his BS degree from the University of Tehran, and his MS and Ph.D. degrees from Caltech.

   He has received several awards for his research including the Ellis Island Medal of Honor, the Pioneer Award in Nanotechnology, the Gold Medal from SPIE, the Balthasar van der Pol Gold Medal from the International Union of Radio Science (URSI), the William Streifer Scientific Achievement Award, induction to the Canadian Academy of Engineering as an International Fellow, the Fellow of US National Academy of Inventors (NAI), the IEEE Electromagnetics Award, the IEEE Antennas and Propagation Society Distinguished Achievement Award, the Beacon of Photonics Industry Award, the Vannevar Bush Faculty Fellowship Award from US Department of Defense, the Wheatstone Lecture in King’s College London, the Inaugural SINA Award in Engineering, 2006 Scientific American Magazine 50 Leaders in Science and Technology, the Guggenheim Fellowship, and the IEEE Third Millennium Medal.

   He is a Fellow of seven international scientific and technical organizations, i.e., IEEE, OSA, APS, MRS, SPIE, URSI, and AAAS. He has received the honorary doctoral degrees from the Aalto University in Finland in 2016, the University of Stuttgart, Germany in 2016, and Ukraine’s National Technical University Kharkov Polytechnic Institute in 2017.

   His current research activities span a broad range of areas including photonics, metamaterials, electrodynamics, nano-optics, graphene photonics, imaging and sensing inspired by eyes of animal species, microwave and optical antennas, and physics and engineering of fields and waves.

   tickets: https://www.eventbrite.com/e/prof-nader-engheta-metaphotonics-osa-annual-lecture-tickets-83770069533

   This event is organised by Imperial College Optics Society, a diverse group of graduate students working in optics who volunteer in the organisation of events such as lectures, seminars and other activities aimed at professional development and outreach in optics and related sciences, sponsored by OSA and SPIE. The Chapter welcomes students from all backgrounds with an interest in the optical sciences. Any further info may be found at: https://www.imperial.ac.uk/photonics/about-us/optical-society/

    

    

9. Quantum light at the nanoscale

   November 20, 2019 4:52 pm Leave a Comment

   Optical realisation of a quantum computer, secure quantum communications and imaging requires fast and reliable generation of single photons and their quantum superpositions. Future quantum optical sources should be small as they will need to be integrated into future photonics devices so that they fit ‘on-chip’.

   When an intense light impinges onto nonlinear material, high energy photons can split into two. This interaction divides their energy, leaving a pair of lower energy photons which are entangled. The first demonstration of a reconfigurable nanoscale light source of entangled two-photon states was realised by the multinational team involving the Photonics & Nanotechnology Group at the Physics Department at King’s College London (King’s).

   Nano-antennas are nanometric material structures that strongly interact with light.  Optical nano-antennas have already shown a great ability to manipulate photons efficiently, but their potential for production of multi-photon quantum states remained unexplored.

   In the framework of a multinational collaboration involving researchers in the UK, Australia, France, Italy and China, Dr Giuseppe Marino, a PhD student from the Photonics & Nanotechnology Group at King’s and current postdoctoral fellow at  Université de Paris, has experimentally demonstrated, the nanoscale generation of two-photon quantum states enhanced by the nanoscale semiconductor antenna. It is also easy to achieve the desired spectral response by changing the nano-antenna shape and geometry.

   When excited by a laser, the nano-antenna generates pairs of photons at a much higher rate than usual methods. The research ‘Spontaneous photon-pair generation from a dielectric nanoantenna is published in Optica.

   These experiments now pave the way to the development of nanoscale structures to generate multi-photon quantum states.  Future applications include secure telecommunications and quantum imaging.

   “Scalable and integratable nanoscale quantum optical sources are a must if the optical quantum technologies will grow from the lab to real-world applications,” says Professor Zayats, a co-author of the paper, “these results show that indeed such miniaturised optical sources can be engineered not only without compromising the performance but actually with better performance than their traditional bulky counterparts”.

   Link to the paper: (doi.org/10.1364/OPTICA.6.001416)

    

10. Seminar – 14 October – Prof. Tuan Vo-Din

    October 8, 2019 3:47 pm Leave a Comment

    Next Monday, 14 October, Dr Manuel Müller will be hosting Prof. Tuan Vo-Dinh (Duke University) who will be delivering a seminar in G8, New Hunt’s House, Guy’s Campus,  King’s College London, SE1 9RT @ 16.30.

     

    Prof. Tuan Vo-Din is in the UK to as the recipient of the 2019 Royal Society of Chemistry Sir George Stokes Medal

    https://www.rsc.org/ScienceAndTechnology/Awards/SirGeorgeStokesAward/2019-Winner.asp

     

    His abstract is below.

     

    Plasmonic Nanosensors and Nanoprobes:   Harnessing the Power of Photonics for Medical Diagnostics and Therapy

     

    This lecture provides an overview of recent developments in our laboratory for several plasmonic nanoplatforms and biosensing technologies that allow biomedical diagnostics from the gene level to single-cell, and whole body systems. Plasmonics refers to the research area of enhanced electromagnetic properties of metallic nanostructures that produce ultrasensitive and selective detection technologies. The technology involves interactions of laser radiation with metallic nanoparticles, inducing very strong enhancement of the electromagnetic field on the surface of the nanoparticles. These processes, often called ‘plasmonic enhancements’, produce the surfaceenhanced Raman scattering (SERS) effect that could enhance the Raman signal of molecules on these nanoparticles more than a million fold.  A SERS-based nanoprobe technology, referred to as ‘Molecular Sentinel’ nanoprobes, has been developed to detect early biomarkers (mRNA, miRNA) of cancer (e.g., BRCA1, ERB2 cancer genes). A unique nanoplatform referred to as gold nanostars, offers plasmon properties that efficiently transduce photon energy into heat for photothermal therapy. Nanostars, with their small core size and multiple long thin branches, exhibit intense two-photon luminescence, and high absorption cross sections that are tunable in the near infrared region with relatively low scattering effect, rendering them efficient efficient photothermal agents in cancer therapy. A theranostics nanoplatform construct was created, allowing SERS imaging and photodynamic therapy. SERSbased plasmonic nanoprobes and nanochip systems have also been developed for use as diagnostic systems for point-of-care personalized nanomedicine and global health applications.  We have recently developed a novel two-pronged modality by merging gold nanostarsenhanced photothermal treatment with checkpoint immunotherapy into a Synergistic Immuno Photothermal Nanotherapy (SYMPHONY), which has the potential to eradicate both primary tumours and ‘untreated’ distant metastatic foci. Delayed rechallenge with repeated bladder and brain cancer cells injections in cured mice did not lead to new tumour formation after several months of observation, indicating that SYMPHONY induced effective long-lasting immunity like an anti-cancer ‘vaccine’ effect against cancer in  murine models.