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  • Journal article
    Byrnes N, Foreman MR, 2022,

    Polarisation statistics of vector scattering matrices from the circular orthogonal ensemble

    , Optics Communications, Vol: 503, Pages: 1-6, ISSN: 0030-4018

    We study the polarisation properties of random𝑁×𝑁scattering matrices distributed according to the circularorthogonal ensemble. We interpret 2×2 sub-blocks of the scattering matrix as Jones matrices and study theirstatistical properties. Using the polar decomposition, we derive probability density functions for retardanceand diattenuation from scattering matrices of arbitrary size and in the limit𝑁→∞.

  • Journal article
    Kalita R, Flanagan W, Lightley J, Kumar S, Alexandrov Y, Garcia E, Hintze M, Barkoulas M, Dunsby C, French PMWet al., 2021,

    Single-shot phase contrast microscopy using polarisation-resolved differential phase contrast

    , JOURNAL OF BIOPHOTONICS, ISSN: 1864-063X
  • Journal article
    Wright T, Sparks H, Paterson C, Dunsby Cet al., 2021,

    Video-rate remote refocusing through continuous oscillation of a membrane deformable mirror

    , Journal of Physics: Photonics, ISSN: 2515-7647

    This paper presents the use of a deformable mirror (DM) configured to rapidly refocus a microscope employing a highnumerical aperture objective lens. An Alpao DM97-15 membrane DM was used to refocus a 40×/0.80 NA water-immersionobjective through a defocus range of -50 to 50 m at 26.3 sweeps per second. We achieved imaging with a mean Strehlmetric of > 0.6 over a field of view in the sample of 200×200 m2 over a defocus range of 77 m. We describe anoptimisation procedure where the mirror is swept continuously in order to avoid known problems of hysteresis associatedwith the membrane DM employed. This work demonstrates that a DM-based refocusing system could in the future be used inlight-sheet fluorescence microscopes to achieve video-rate volumetric imaging.

  • Journal article
    Geberbauer J, Kerridge-Johns W, Damzen M, 2021,

    > 30 W vortex LG₀₁ or HG₁₀ laser using a modetransforming output coupler

    , Optics Express, Vol: 29, Pages: 29082-29094, ISSN: 1094-4087

    High-power vortex light generated directly from lasers will help drive theirapplications in material processing, optical manipulation, levitation, particle acceleration, andcommunications, but limited power has been achieved to date. In this work, we demonstraterecord vortex average power of 31.3 W directly from a laser, to the best of our knowledge,using an interferometric mode transforming output coupler to convert a fundamental modeNd:YVO4 laser into a LG01 vortex output. The vortex laser was Q-switched with up to 600 kHzpulse rate with a high slope efficiency of 62.5% and an excellent LG01 modal purity of 95.2%.We further demonstrate > 30W laser power in a high quality HG10 mode by simple adjustmentof the output coupler. Experimental investigations of varying output coupling transmission arecompared with theory. This successful implementation of the interferometric output coupler ina high power system demonstrates the suitability of the mode transforming method for robustturn-key vortex lasers with high efficiency and high modal purity, with scalable power andpulse rate.

  • Journal article
    Paraiso TK, Woodward R, Marangon DG, Lovic V, Yuan Z, Shields AJet al., 2021,

    Advanced Laser Technology for Quantum Communications (Tutorial Review)

    , ADVANCED QUANTUM TECHNOLOGIES
  • Journal article
    Lightley J, Gorlitz F, Kumar S, Kalita R, Kolbeinsson A, Garcia E, Alexandrov Y, Bousgouni V, Wysoczanski R, Barnes P, Donnelly L, Bakal C, Dunsby C, Neil MAA, Flaxman S, French PMWet al., 2021,

    Robust deep learning optical autofocus system applied to automated multiwell plate single molecule localization microscopy

    , JOURNAL OF MICROSCOPY, ISSN: 0022-2720
  • Journal article
    Berk J, Foreman MR, 2021,

    Role of multiple scattering in single particle perturbations in absorbing random media

    , Physical Review Research, Vol: 3, Pages: 1-14, ISSN: 2643-1564

    Speckle patterns produced by disordered scattering systems exhibit asensitivity to addition of individual particles which can be used for sensingapplications. Using a coupled dipole model we investigate how multiplescattering can enhance field perturbations arising in such random scatteringbased sensors. Three distinct families of multiple scattering paths are shownto contribute and the corresponding complex enhancement factors derived.Probability distributions of individual enhancement factors over the complexplane are characterised numerically within the context of surface plasmonpolariton scattering in which absorption is shown to play an important role. Weshow that enhancements become more strongly dependent on individual scattererproperties when absorption losses are larger, however, amplitude enhancements$\sim 10^2$, comparable to low loss surface plasmons, are achievable throughsensor optimisation. Approximate analytic expressions for the complex meanenhancements are also found, which agree well with simulations when loopcontributions are negligible.

  • Conference paper
    Garcia E, Lightley J, Kumar S, Kalita R, Gorlitz F, Alexandrov Y, Cook T, Dunsby C, Neil M, Roufosse C, French Pet al., 2021,

    Application of direct stochastic optical reconstruction microscopy (dSTORM) to the histological analysis of human glomerular disease

    , Publisher: SPRINGER, Pages: S142-S142, ISSN: 0945-6317
  • Journal article
    Gratus J, Seviour R, Kinsler P, Jaroszynski DAet al., 2021,

    Temporal boundaries in electromagnetic materials

    , NEW JOURNAL OF PHYSICS, Vol: 23, ISSN: 1367-2630
  • Journal article
    Berk J, Foreman MR, 2021,

    Theory of multiple scattering enhanced single particle plasmonic sensing

    , ACS Photonics, Vol: 8, Pages: 2227-2233, ISSN: 2330-4022

    Methods to increase the light scattered from small particles can help improve the sensitivity of many sensing techniques. Here, we investigate the role multiple scattering plays in perturbing the scattered signal when a particle is added to a random scattering environment. Three enhancement factors, parametrizing the effect of different classes of multiple scattering trajectories on the field perturbation, are introduced and their mean amplitudes explored numerically in the context of surface plasmon polariton scattering. We demonstrate that there exists an optimum scatterer density at which the sensitivity enhancement is maximized, with factors on the order of 102 achievable. Dependence of the enhancement factors on scatterer properties are also studied.

  • Journal article
    Pittaluga M, Minder M, Lucamarini M, Sanzaro M, Woodward RI, Li MJ, Yuan Z, Shields AJet al., 2021,

    600-km repeater-like quantum communications with dual-band stabilization

    , Nature Photonics, Vol: 15, Pages: 530-535, ISSN: 1749-4885

    Twin-field (TF) quantum key distribution (QKD) fundamentally alters the rate-distance relationship of QKD, offering the scaling of a single-node quantum repeater. Although recent experiments have demonstrated the new opportunities for secure long-distance communications allowed by TF-QKD, formidable challenges remain to unlock its true potential. Previous demonstrations have required intense stabilization signals at the same wavelength as the quantum signals, thereby unavoidably generating Rayleigh scattering noise that limits the distance and bit rate. Here, we introduce a dual-band stabilization scheme that overcomes past limitations and can be adapted to other phase-sensitive single-photon applications. Using two different optical wavelengths multiplexed together for channel stabilization and protocol encoding, we develop a setup that provides repeater-like key rates over communication distances of 555 km and 605 km in the finite-size and asymptotic regimes respectively and increases the secure key rate at long distance by two orders of magnitude to values of practical relevance.

  • Journal article
    De Marco I, Woodward RI, Roberts GL, Paraiso TK, Roger T, Sanzaro M, Lucamarini M, Yuan Z, Shields AJet al., 2021,

    Real-Time operation of a multi-rate, multi-protocol quantum key distribution transmitter

    , Optica, Vol: 8, Pages: 911-915, ISSN: 2334-2536

    Quantum key distribution (QKD) is the best candidate for securing communications against attackers, who may in the future exploit quantum-enhanced computational powers to break classical encryption. As such, new challenges are arising from our need for large-scale deployment of QKD systems. In a realistic scenario, transmitting and receiving devices from different vendors should be able to communicate with each other without the need for matching hardware. Therefore, practical deployment of QKD would require hardware capable of adapting to different protocols and clock rates. Here, we address this challenge by presenting a multi-rate, multi-protocol QKD transmitter linked to a correspondingly adaptable QKD receiver. The flexibility of the transmitter, achieved by optical injection locking, allows us to connect it with two receivers with inherently different clock rates. Furthermore, we demonstrate the multi-protocol operation of our transmitter, communicating with receiving parties employing different decoding circuits. Published by The Optical Society under the terms of the Creative Commons Attribution 4.0 License.

  • Journal article
    Berk J, Paterson C, Foreman MR, 2021,

    Tracking single particles using surface plasmon leakage radiation speckle

    , Journal of Lightwave Technology, Vol: 39, Pages: 3950-3960, ISSN: 0733-8724

    Label free tracking of small bio-particles such as proteins or viruses is of great utility in the study of biological processes, however such experiments are frequently hindered by weak signal strengths and a susceptibility to scattering impurities. To overcome these problems we here propose a novel technique leveraging the enhanced sensitivity of both interferometric detection and the strong field confinement of surface plasmons. Specifically, we show that interference between the field scattered by an analyte particle and a speckle reference field, derived from random scattering of surface plasmons propagating on a rough metal film, enables particle tracking with sub-wavelength accuracy. We present the analytic framework of our technique and verify its robustness to noise through Monte Carlo simulations.

  • Journal article
    Boland MA, Cohen EAK, Flaxman SR, Neil MAAet al., 2021,

    Improving axial resolution in Structured Illumination Microscopy using deep learning

    , PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES, Vol: 379, ISSN: 1364-503X
  • Journal article
    Gong H, Guo W, Neil MAA, 2021,

    GPU-accelerated real-time reconstruction in Python of three-dimensional datasets from structured illumination microscopy with hexagonal patterns

    , PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES, Vol: 379, ISSN: 1364-503X
  • Journal article
    Garcia E, Lightley J, Kumar S, Kalita R, Gorlitz F, Alexandrov Y, Cook T, Dunsby C, Neil MAA, Roufosse CA, French PMWet al., 2021,

    Application of direct stochastic optical reconstruction microscopy (dSTORM) to the histological analysis of human glomerular disease

    , JOURNAL OF PATHOLOGY CLINICAL RESEARCH, Vol: 7, Pages: 438-445
  • Journal article
    Cannon T, Lagarto J, Dyer B, Garcia Castano E, Kelly D, Peters N, Lyon A, French P, Dunsby Cet al., 2021,

    Characterisation of NADH fluorescence properties under one-photon excitation with respect to temperature, pH and binding to lactate dehydrogenase

    , Optical Society of America Continuum, Vol: 4, Pages: 1610-1625

    Reduced nicotinamide adenine dinucleotide (NADH) is the principal electron donor in glycolysis and oxidative metabolism and is thus recognized as a key biomarker for probing metabolic state. While the fluorescence characteristics of NADH have been investigated extensively, there are discrepancies in the published data due to diverse experimental conditions, instrumentation and microenvironmental parameters that can affect NADH fluorescence. Using a cuvette-based time-resolved spectrofluorimeter employing one-photon excitation at 375 nm, we characterized the fluorescence intensity, lifetime, spectral response, anisotropy and time-resolved anisotropy of NADH in aqueous solution under varying microenvironmental conditions, namely temperature, pH, and binding to lactate dehydrogenase (LDH). Our results demonstrate how temperature, pH, and binding partners each impact the fluorescence signature of NADH and highlight the complexity of the fluorescence data when different parameters produce competing effects. We hope that the data presented in this study will provide a reference for potential sources of variation in experiments measuring NADH fluorescence.

  • Journal article
    Azeem F, Trainor LS, Devane PA, Norman DS, Rueda A, Lambert NJ, Kumari M, Foreman MR, Schwefel HGLet al., 2021,

    Dielectric perturbations: anomalous resonance frequency shifts in optical resonators

    , Optics Letters, Vol: 46, Pages: 2477-2480, ISSN: 0146-9592

    Small perturbations in the dielectric environment around resonant dielectric structures usually lead to a frequency shift of the resonator modes directly proportional to the polarizability of the perturbation. Here, we report experimental observations of strong frequency shifts that can oppose and even exceed the contribution of the perturbations’ polarizability. We show in particular how the mode frequencies of a lithium niobate whispering-gallery-mode resonator are shifted by planar substrates—of refractive indices ranging from 1.50 to 4.22—contacting the resonator rim. Both blue- and redshifts are observed, as well as an increase in mode linewidth, when substrates are moved into the evanescent field of the whispering gallery mode. We compare the experimental results to a theoretical model by Foreman et al. [J. Opt. Soc. Am. B 33, 2177 (2016) [CrossRef] ] and provide an additional intuitive explanation based on the Goos–Hänchen shift for the optical domain, with applications to dielectric structures ranging from meta-surfaces to photonic crystal cavities.

  • Journal article
    Gratus J, Kinsler P, McCall MW, 2021,

    Temporary Singularities and Axions: An Analytic Solution that Challenges Charge Conservation

    , ANNALEN DER PHYSIK, Vol: 533, ISSN: 0003-3804
  • Journal article
    Murray RT, Chandran AM, Battle RA, Runcorn TH, Schunemann PG, Zawilski KT, Guha S, Taylor JRet al., 2021,

    Seeded optical parametric generation in CdSiP2 pumped by a Raman fiber amplifier at 124  µm

    , Optics Letters, Vol: 46, Pages: 2039-2039, ISSN: 0146-9592

    We report a seeded optical parametric generator (OPG) producing tunable radiation from 4.2–4.6 µm. The seeded OPG employs a 13 mm long CdSiP2 (CSP) crystal cut for non-critical phase-matching, pumped by a nanosecond-pulsed, MHz repetition rate Raman fiber amplifier system at 1.24 µm. A filtered, continuous-wave fiber supercontinuum source at 1.72 µm is used as the seed. The source generates up to 0.25 W of mid-infrared (MIR) idler power with a total pump conversion of 42% (combined signal and idler).

  • Journal article
    Kerridge-Johns WR, Jaillot J-B, Damzen MJ, 2021,

    Sampling a vortex from a Gaussian beam using a wedge-plate shearing interferometer

    , Applied Optics, Vol: 60, Pages: 3510-3510, ISSN: 1559-128X

    Many vortex-generation techniques have been developed to address a range of potential applications, exploiting their unique amplitude and phase profiles and their possession of orbital angular momentum. In this work, we present what may be the simplest method of vortex beam generation, requiring only a wedged optic: the wedge-plate shearing interferometer (WPSI). We show that the WPSI can reflect a first order Laguerre–Gaussian vortex beam (LG01) with a theoretical purity of >99% from an input fundamental Gaussian beam, with 98% LG01 purity experimentally demonstrated. We demonstrate 1% power conversion with a route to 14%. The monolithic WPSI is a simple, compact, and highly stable device, which can operate at any wavelength that the material is transparent to. We anticipate that it will be useful where sampling a robust, high-purity vortex beam from a Gaussian laser beam is required, including low-cost vortex generation for metrology or education.

  • Conference paper
    Dvinskikh L, Harding S, Sparks H, Gorelik J, MacLeod K, Dunsby Cet al., 2021,

    High speed imaging of calcium dynamics in cardiomyocytes with a flexible light-sheet fluorescence microscope

    , Biophotonics Congress 2021
  • Journal article
    Woodward RI, Lo YS, Pittaluga M, Minder M, Paraiso TK, Lucamarini M, Yuan ZL, Shields AJet al., 2021,

    Gigahertz measurement-device-independent quantum key distribution using directly modulated lasers

    , NPJ QUANTUM INFORMATION, Vol: 7
  • Journal article
    Xiang Y, Seow KLC, Paterson C, Torok Pet al., 2021,

    Multivariate analysis of Brillouin imaging data by supervised and unsupervised learning

    , JOURNAL OF BIOPHOTONICS, ISSN: 1864-063X
  • Journal article
    Collart C, Ciccarelli A, Ivanovitch K, Rosewell I, Kumar S, Kelly G, Edwards A, Smith JCet al., 2021,

    The migratory pathways of the cells that form the endocardium, dorsal aortae, and head vasculature in the mouse embryo

    , BMC DEVELOPMENTAL BIOLOGY, Vol: 21, ISSN: 1471-213X
  • Conference paper
    Murray RT, Chandran AM, Battle RA, Runcorn TH, Schunemann PG, Zawilski KT, Guha S, Taylor JRet al., 2021,

    Seeded optical parametric generation in CdSiP2 pumped by a nanosecond pulsed, MHz repetition rate Raman fiber amplifier at 1.24 µm

    , Nonlinear Frequency Generation and Conversion: Materials and Devices XX, Publisher: SPIE, Pages: 1-10

    We report a CdSiP2 (CSP) based seeded optical parametric generator (OPG), emitting sub-nanosecond duration, 3 MHz repetition rate, wavelength tunable mid-infrared (MIR) light at 4.2-4.6 μm. We generate up to 0.25 W at 4.2 μm with a total pump conversion efficiency of 42%. The OPG is pumped by a 1.24 μm Raman fiber amplifier system. This is the first demonstration of pumping CSP with a Raman fiber source in this region, and we show that Raman fiber sources in the near-infrared (NIR) are ideal pump sources for non-critically phasematched (NCPM) CSP devices. Pumping CSP at 1.24 μm permits the use of NCPM whilst decreasing the negative effects of both two-photon absorption and linear absorption losses, when compared to conventional 1 μm pumping. This offers a potential advantage for MIR power scaling of CSP parametric devices due to a reduced thermal load in the crystal from residual pump absorption. The OPG is seeded with a continuous-wave fiber supercontinuum source emitting radiation in the 1.7 μm region, to lower the threshold pump intensity required for efficient conversion. NCPM and temperature tuning of the crystal allow for simple wavelength tuning of the idler radiation. We report on laser damage induced by elevated crystal temperatures, which we propose is linked to the decrease in CSP bandgap energy with increasing temperature.

  • Journal article
    Kondo H, Ratcliffe CDH, Hooper S, Ellis J, MacRae J, Hennequart M, Dunsby CW, Anderson K, Sahai Eet al., 2021,

    Single-cell resolved imaging reveals intra-tumor heterogeneity in glycolysis, transitions between metabolic states, and their regulatory mechanisms

    , CELL REPORTS, Vol: 34, ISSN: 2211-1247
  • Journal article
    Byrnes N, Foreman MR, 2021,

    Symmetry constraints for vector scattering and transfer matrices containing evanescent components: energy conservation, reciprocity and time reversal

    , Physical Review Research, Vol: 3, Pages: 013129 – 1-013129 – 13, ISSN: 2643-1564

    In this work we study the scattering and transfer matrices for electricfields defined with respect to an angular spectrum of plane waves. For thesematrices, we derive the constraints that are enforced by conservation ofenergy, reciprocity and time reversal symmetry. Notably, we examine the generalcase of vector fields in three dimensions and allow for evanescent fieldcomponents. Moreover, we consider fields described by both continuous anddiscrete angular spectra, the latter being more relevant to practicalapplications, such as optical scattering experiments. We compare our results tobetter-known constraints, such as the unitarity of the scattering matrix forfar-field modes, and show that previous results follow from our framework asspecial cases. Finally, we demonstrate our results numerically with a simpleexample of wave propagation at a planar glass-air interface, including theeffects of total internal reflection. Our formalism makes minimal assumptionsabout the nature of the scattering medium and is thus applicable to a widerange of scattering problems.

  • Working paper
    Kinsler P, 2021,

    A new introduction to spatial dispersion: Reimagining the basic concepts

    , Publisher: ELSEVIER
  • Journal article
    Jones DC, Alexandrov Y, Curry N, Kumar S, Lanigan PMP, McGuinness CD, Dale MW, Twitchen DJ, Fisher D, Neil MAA, Dunsby C, French PMWet al., 2021,

    Multidimensional spectroscopy and imaging of defects in synthetic diamond: excitation-emission-lifetime luminescence measurements with multiexponential fitting and phasor analysis

    , Journal of Physics D: Applied Physics, Vol: 54, Pages: 1-13, ISSN: 0022-3727

    We report the application of phasor analysis and nonlinear iterative fitting to complex spatial and spectroscopic luminescence decay data obtained from multidimensional microscopy of a CVD diamond grown on a HPHT substrate. This spectral and lifetime-resolved analysis enabled spatial mapping of variations in concentrations of nitrogen vacancy (NV) defects in both charge states and the quenching of NV− defects, as well as the identification of SiV− luminescence. These imaging and spectroscopic modalities may be important for reliable fabrication of quantum devices based on such defects in diamond, which will require well-defined and characterised quantum electronic properties.

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