Nikolay I. Zheludev

Using a nanowire as example, we experimentally demonstrate all-optical metrology with resolution up to 80 pm and sampling rate up to 1M fps. Here, topologically structured light scattering is used to visualize nanoobject’s trajectory with an algorithm discriminating instrumental instabilities and movements of the object relative to its immediate environment.

Using nano-opto-mechanical platform we demonstrate a new class of photonic materials in which illumination with light creates nonreciprocal interactions that spontaneously breaks continuous space and time translation symmetries into discrete translation symmetries.

It is now well understood from the works on topology of light, that complex optical fields (e.g. superoscillatory fields) can be structured at deeply subwavelength scales. Point-like singularities, zones of energy back-flow and strong variations of phase and intensity can be orders of magnitude smaller than the wavelength. As such, scattering of light on nanoscale objects can strongly depend on exactly where the object is actually located in the structured field. This is the foundational idea of metrology with topologically structured light.Moreover, in localization metrology the use of artificial intelligence in the analysis of scattered light allows for instrumental fluctuations and drifts in the whole sample position to be distinguished from the displacements of the nanoscale object with respect to its immediate environment.Furthermore, we demonstrate that ultrafast cameras allow atomic level metrology with a rate of one million measurements per second which gives access to the studies of dynamical processes such as driven or thermal motion in nanostructures.

This dataset supports the following publication: Shen, Y., Hou, Y., Papasimakis, N. et al. Supertoroidal light pulses as electromagnetic skyrmions propagating in free space. Nat Commun 12, 5891 (2021). https://doi.org/10.1038/s41467-021-26037-w This dataset contains: - Fig. 1 presents plots of the spatial profiles of the real parts of electric fields of Equation (4) of the two pulses of α=1 and α=5 for q2=100q1 and t = 0, ±q2/(4c), and ±q2/(2c). - Fig. 2a-b present plots of the isoline plots of the electric fields of Equation (4) in the x-z plane for the two pulses shown in Fig.1. - Fig. 3a-b present plots of isoline and arrow plots of the magnetic fields of Equations (5,6) in the x-z plane for the two pulses shown in Fig.1. - Fig. 4a-b present plots of contour and arrow plots of the Poynting vector fields in the x-z plane for the two pulses shown in Fig.1. - Fig. 5a-b present plots of the isoline plot of the logarithm distributions of electric and magnetic fields in the x-z plane for for the pulse of the real part of Equations (4-6) for q2=100q1, t = 0, and α=20. - Fig. 6a-b presents the numbers and positions (a and b) of on-axis saddle-singularities of the magnetic field of the pulse in Fig.5 within the range of z 2 [0; 80q1], versus α. The authors acknowledge the supports of the MOE Singapore (MOE2016-T3-1-006), the UKs Engineering and Physical Sciences Research Council (grant EP/M009122/1, Funder Id: http://dx.doi.org/10.13039/501100000266), the European Research Council (Advanced grant FLEET-786851, Funder Id: http://dx.doi.org/10.13039/501100000781), and the Defense Advanced Research Projects Agency (DARPA) under the Nascent Light Matter Interactions …

Nonreciprocal nonequilibrium process are attracting growing interest in sociology, animal behaviour, chemistry, and nanotechnology, and may have played a role in the origin of life. It is less widely recognized, however, that in open systems light can induce nonreciprocal predator-prey like forces between nanoparticles. Such forces provide access to the continuous time crystal state of matter, which has been demonstrated in a plasmonic metamaterial array of nanowires wherein light triggers a spontaneous mobilization transition to the robust oscillatory state, breaking time translation symmetry. Here, we report on the first experimental study of the transient dynamics of light-induced mobilization and demobilization in a time crystal. By analysing time resolved phase trajectories of the system of nanowires, we show that the mobilization transition is accompanied by breaking of continuous time translation symmetry and ergodicity, and a decrease in the entropy of motion. This insight into the transient dynamics of a nonreciprocity-driven time crystal is relevant to optical timetronics, an information and communications technology paradigm relying on the unique functionalities of time crystals, and applications of the interacting nanowire oscillator platform to modelling a wide range of nonreciprocal processes from many-body dynamics to the early stages of matter-to-life transitions.

Distinguishing two objects or point sources located closer than the Rayleigh distance is impossible in conventional microscopy. Understandably, the task becomes increasingly harder with a growing number of particles placed in close proximity. It has been recently demonstrated that subwavelength nanoparticles in closely packed clusters can be counted by AI-enabled analysis of the diffraction patterns of coherent light scattered by the cluster. Here, we show that deep learning analysis can return the actual positions of nanoparticles in the cluster. The Pearson correlation coefficient between the ground truth and reconstructed positions of nanoparticles exceeds 0.7 for clusters of ten nanoparticles and 0.8 for clusters of two nanoparticles of 0.16 k in diameter, even if they are separated by distances below the Rayleigh resolution limit of 0.68 k, corresponding to a lens with numerical aperture NA ¼ 0.9.

Metasurfaces have recently risen to prominence in optical research, providing unique functionalities that can be used for imaging, beam forming, holography, polarimetry, and many more, while keeping device dimensions small. Despite the fact that a vast range of basic metasurface designs has already been thoroughly studied in the literature, the number of metasurface-related papers is still growing at a rapid pace, as metasurface research is now spreading to adjacent fields, including computational imaging, augmented and virtual reality, automotive, display, biosensing, nonlinear, quantum and topological optics, optical computing, and more. At the same time, the ability of metasurfaces to perform optical functions in much more compact optical systems has triggered strong and constantly growing interest from various industries that greatly benefit from the availability of miniaturized, highly functional, and efficient …

Metastable optically controlled devices (optical flip‐flops) are needed in data storage, signal processing, and displays. Although nonvolatile memory relying on phase transitions in chalcogenide glasses has been widely used for optical data storage, beyond that, weak optical nonlinearities have hindered the development of low‐power bistable devices. This work reports a new type of volatile optical bistability in a hybrid nano‐optomechanical device, comprising a pair of anchored nanowires decorated with plasmonic metamolecules. The nonlinearity and bistability reside in the mechanical properties of the acoustically driven nanowires and are transduced to the optical response by reconfiguring the plasmonic metamolecules. The device can be switched between bistable optical states with microwatts of optical power and its volatile memory can be erased by removing the acoustic signal. The demonstration of …

Nano-opto-mechanical metamaterials on semiconductor nanomembranes are a perfect platform for parametric optical devices, frequency mixing and optical comb generation, and fundamental studies of coupling between thermal excitations in metamaterials and their optical properties.

Understanding the nanoscale behavior of helicity-dependent photocurrents is important to understand light-matter interaction in structured topological materials. Here we report direct nanoimaging of the distribution of circular polarization dependent surface currents on nanostructured topological insulators.

Despite recent tremendous progress in optical imaging and metrology, , , , –, there remains a substantial resolution gap between atomic-scale transmission electron microscopy and optical techniques. Is optical imaging and metrology of nanostructures exhibiting Brownian motion possible with such resolution, beyond thermal fluctuations? Here we report on an experiment in which the average position of a nanowire with a thermal oscillation amplitude of ∼150 pm is resolved in single-shot measurements with subatomic precision of 92 pm, using light at a wavelength of λ = 488 nm, providing an example of such sub-Brownian metrology with ∼λ/5,300 precision. To localize the nanowire, we employ a deep-learning analysis of the scattering of topologically structured light, which is highly sensitive to the nanowire’s position. This non-invasive metrology with absolute errors down to a fraction of the typical size of an …

We report a new light absorption device that - in principle - can absorb light completely across the entire electromagnetic spectrum by utilizing its spatial coherence and we provide proof-of-concept experimental demonstration of such a device. Complete absorption of broadband light is key for several technologies including photovoltaics, energy conversion, quantum and stealth technologies. We demonstrated broadband coherent perfect absorption through experimental results. Constructive interference of counterpropagating waves on a thin film with appropriate optical properties (e.g. chromium or graphene film of appropriate thickness with 50% absorption) enables complete (deterministic) absorption of light, down to the single-photon level. We, recently, succeeded in demonstrating experimentally how this discovery can be utilized to realize a compact device that perfectly absorbs broadband spectrum of light simultaneously- by broadband constructive interference of light we achieved perfect absorption in nanometer scale thin films. When the optical path lengths were not matched, the reflectivity spectrum oscillated between coherent absorption and coherent transmission. With alignment, the bandwidth of coherent absorption increased, and became very large when the path lengths were matched. In this case, we observed only 9% reflectivity across the studied wavelength range of 1540 to 1620 nm, implying >90% absorption. Changing one effective optical path length by about half a wavelength switched between coherent absorption and coherent transmission of the Cr film, i.e., between a perfect absorber and a mirror. We also note that …

Picometer-scale events in the nanoworld can be monitored with topologically structured light, while light-induced interactions and picometric movements can underpin time crystals—a new form of functional photonic material.

Experimental data presented in the paper published in Nature Physics: Photonic metamaterial analogue of a continuous time crystal, Tongjun Liu, Jun-Yu. Ou, Kevin F. MacDonald, Nikolay I. Zheludev, Nat. Phys.

Continuous time crystals (CTCs) - media with broken continuous time translation symmetry - are an eagerly sought state of matter that spontaneously transition from a time-independent state to one of periodic motion in response to a small perturbation. The state has been realized recently in an array of nanowires decorated with plasmonic metamolecules illuminated with light. Here we show that this as-yet-unexplained CTC state can be understood as arising from a nonreciprocal phase transition induced by nonconservative radiation pressure forces among plasmonic metamolecules: above a certain intensity threshold, light drives the inhomogeneously broadened array of thermally-driven noisy nanowire oscillators to a synchronized coherent space-time crystal state and ergodicity of the system is broken. At the onset of synchronization, this mechanism does not require nonlinearity in the oscillators but depends instead on nonreciprocal forces. As such it is fundamentally different from the regimes of synchronization that depend on nonlinearity.

Direct nanoimaging of helicity-dependent photocurrents is important to understand light-matter interaction in topological materials. Here we report visualization of circular polarization dependent surface currents and their distribution on plain and artificially nanostructured topological insulators.

We introduce a new ‘optical ruler’ concept, which allows for single-shot, real-time detection of nanometric displacements down to λ/400, through the visualization of singularities in a topologically structured optical field using a polarization-sensitive camera.

We demonstrate a new imaging paradigm based on multipole decomposition tomography of light scattered on the imaged object and conduct proof of principle experiments that show the accurate quantification of weaker radiation below the conventional detectable range limited by accompanying stronger radiation.

Quantum tomography is one of the major challenges of large-scale quantum information research due to the exponential time complexity. In this Letter, we develop and apply a Bayesian state estimation method to experimentally demonstrate quantum overlapping tomography [Phys. Rev. Lett. 124, 100401 (2020)], a scheme intent on characterizing critical information of a many-body quantum system in logarithmic time complexity. By comparing the measurement results of full-state tomography and overlapping tomography, we show that overlapping tomography gives accurate information of the system with much fewer state measurements than full-state tomography.

Time crystals are an eagerly sought phase of matter in which time-translation symmetry is broken. Quantum time crystals with discretely broken time-translation symmetry have been demonstrated in trapped ions, atoms and spins while continuously broken time-translation symmetry has been observed in anatomic condensate inside an optical cavity. Here we report that a classical metamaterial nanostructure, a two-dimensional array of plasmonic metamolecules supported on flexible nanowires, can be driven to a state possessing all key features of a continuous time crystal: continuous coherent illumination by light resonant with the metamolecules’ plasmonic mode triggers a spontaneous phase transition to a superradiant-like state of transmissivity oscillations resulting from many-body interactions among the metamolecules, and which is characterized by long-range order in space and time. As the state can be manipulated optically, the phenomenon is of interest to topological and non-Hermitian physics and applications in frequency conversion, memory, modulation, nonreciprocity and amplification.