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  • Journal article
    Koufidis SF, Koutserimpas TT, Monticone F, McCall MWet al., 2024,

    Electromagnetic wave propagation in time-periodic chiral media

    , Optical Materials Express, Vol: 14, Pages: 3006-3006

    <jats:p>Within the framework of coupled-wave theory, we investigate the propagation of light in a time-periodic chiral medium whose permittivity, permeability, and chirality parameter are periodic functions of time. For non-constant impedance, we show that two first-order momentum gaps emerge in the Brillouin diagram, resulting in parametric amplification with distinct amplification factors and corresponding momenta for right- and left-handed modes. The presence of chirality plays a pivotal role in manipulating lightwave signals, controlling the center of resonance, the corresponding bandgap size, and the amplification factor in a unique manner for each handedness. For a finite “time-slab” of the considered medium, we analytically derive the scattering coefficients as functions of both time and momentum. Additionally, we discuss how extreme values of optical rotation grant access to the temporal analog of the chirality-induced negative refraction regime. Finally, we elucidate the mechanism by which the orientation of the electric field, associated with elliptical polarizations, is altered as the wave propagates within a first-order momentum gap, thereby undergoing simultaneous optical rotation and parametric amplification.</jats:p>
  • Journal article
    Tan Q, Riemer K, Hansen-Shearer J, Yan J, Toulemonde M, Taylor L, Yan S, Dunsby C, Weinberg PD, Tang M-Xet al., 2024,

    Transcutaneous imaging of rabbit kidney using 3-D acoustic wave sparsely activated localization microscopy with a row-column-addressed array

    , IEEE Transactions on Biomedical Engineering, Vol: 71, Pages: 3446-3456, ISSN: 0018-9294

    Objective: Super-resolution ultrasound (SRUS) imaging through localizing and tracking microbubbles, also known as ultrasound localization microscopy (ULM), can produce sub-diffraction resolution images of micro-vessels. We have recently demonstrated 3-D selective SRUS with a matrix array and phase change contrast agents (PCCAs). However, this method is limited to a small field of view (FOV) and by the complex hardware required. Method: This study proposed 3-D acoustic wave sparsely activated localization microscopy (AWSALM) using PCCAs and a 128+128 row-column-addressed (RCA) array, which offers ultrafast acquisition with over 6 times larger FOV and 4 times reduction in hardware complexity than a 1024-element matrix array. We first validated this method on an in-vitro microflow phantom and subsequently demonstrated non-invasively on a rabbit kidney in-vivo. Results: Our results show that 3-D AWSALM images of the phantom covering a 25×25×40 mm 3 volume can be generated under 5 seconds with an 8 times resolution improvement over the system point spread function. The full volume of the rabbit kidney can be covered to generate 3-D microvascular structure, flow speed and direction super-resolution maps under 15 seconds, combining the large FOV of RCA with the high resolution of SRUS. Additionally, 3-D AWSALM is selective and can visualize the microvasculature within the activation volume and downstream vessels in isolation. Sub-sets of the kidney microvasculature can be imaged through selective activation of PCCAs. Conclusion: Our study demonstrates large FOV 3-D AWSALM using an RCA probe. Significance: 3-D AWSALM offers an unique in-vivo imaging tool for fast, selective and large FOV vascular flow mapping.
  • Journal article
    Koufidis SF, Lakhtakia A, McCall MW, 2024,

    Comment on ‘No circular birefringence exists in a chiral medium: an analysis of single-mode refraction’

    , New Journal of Physics, Vol: 26, Pages: 128001-128001

    <jats:title>Abstract</jats:title> <jats:p>Recent claims by Hu and Li (2023 <jats:italic>New J. Phys.</jats:italic> <jats:bold>25</jats:bold> 023007) that isotropic chiral mediums do not exhibit circular birefringence, asserting that both mutually orthogonal circularly polarized states propagate at the same phase velocity, are refuted. We showcase that the analysis is flawed because it incorrectly interprets the eigenstates supported by reciprocal bi-isotropic mediums.</jats:p>
  • Journal article
    Xiao H, Damzen MJ, 2024,

    High-efficiency 5-watt wavelength-tunable UV output from an Alexandrite laser

    , Applied Physics B: Lasers and Optics, Vol: 130, ISSN: 0946-2171

    We investigate the performance of continuous-wave wavelength-tunable ultraviolet output from a diode-pumped Alexandrite laser by intra-cavity second harmonic generation. At 385 nm, ultraviolet output power of 5.05 W is achieved which is the highest continuous-wave ultraviolet power to date for intra-cavity frequency doubled diode-pumped Alexandrite lasers and highest optical-to-optical efficiency of 16.2% is achieved with respect to absorbed red pump power. An excellent ultraviolet wavelength tunable range, 38 nm, is achieved from 364 nm to 402 nm. Cavity mode analysis is performed for design of the resonator including cavity analysis and the modelling of output power from this wavelength tunable ultraviolet laser.
  • Journal article
    Bharadwaj A, Kumar A, Kalita R, MITRA R, Sharma A, Jaganathan BG, Bhattacharyya J, Sarma A, Garcia E, Kumar S, Lightley J, Alexandrov Y, Dunsby C, Neil M, French PMW, Boruah BRet al., 2024,

    Super-resolved fluorescence imaging utilising accessible stochastic optical reconstruction microscopy (easySTORM) implemented on a low-cost, modular open-source (openFrame) microscope

    , Measurement Science and Technology, Vol: 35, ISSN: 0957-0233

    Optical super-resolution microscope is a powerful tool for the life sciences, including cell biology and pathology yielding information on, e.g. biological structure and protein distribution in the nano-scale range. In recent years, there has been an exponential rise in the interest to apply super-resolution microscopes in diverse areas, but its wider utility is hindered by the cost of purchasing and maintaining super-resolved microscopes. In this paper we present the implementation of easySTORM, an accessible implementation of stochastic optical reconstruction microscopy (STORM) at Indian Institute of Technology Guwahati (IITG), India, in a flexible, user friendly and cost-effective manner using a state-of-the-art, modular, open-source, optical microscope platform called: 'openFrame'. Providing comparable imaging performance to commercial optical super-resolution microscopes, the openFrame-based implementation of easySTORM uses in-expensive multimode diode lasers and industry grade CMOS cameras, and the open-source and modular nature of the instrument makes it easy to maintain and to upgrade. To demonstrate its successful implementation at IITG, we image quantum dots and actin-tubulin structure in both normal and cancer cells, resolved features separated by a few tens of nanometers. This work demonstrates that openFrame-enabled easySTORM instrumentation can be widely accessible to provide affordable, research grade super-resolution microscopy capability for academic and medical research.
  • Journal article
    De Corte A, Koufidis SF, McCall MW, Maes Bet al., 2024,

    Exceptional points in negatively refracting chirowaveguides due to giant chirality

    , Physical Review A, Vol: 110, ISSN: 2469-9926
  • Journal article
    Koufidis SF, Koutserimpas TT, Monticone F, McCall MWet al., 2024,

    Enhanced scattering from an almost-periodic optical temporal slab

    , Physical Review A, Vol: 110, ISSN: 2469-9926

    We showcase the impact of almost-periodicity on the parametric amplification associated with the first-order momentum gap in photonic time-crystals with time-varying permittivity. Utilizing a vectorial coupled-wave theory approach, we rigorously analyze the scattering by a temporal slab of the considered medium. We pinpoint a critical regime wherein flaws in material tuning paradoxically enhance amplification due to the coupling of fewer, broader modes, resulting in a higher and broader pulselike amplification envelope. Additionally, we demonstrate that the intensity reflectances of time-reversed waves corresponding to secondary "Bragg"resonances achieve remarkably high levels of subharmonic parametric amplification, with the epsilon-near-zero regime serving as a preferred candidate for experimental implementation. Our counterintuitive findings highlight the potential of intentionally leveraging modulation desynchronization and impurities in the temporal unit cell of photonic time-crystals to enhance both the level and the bandwidth of amplification.
  • Conference paper
    Koufidis SF, Koutserimpas TT, Monticone F, McCall MWet al., 2024,

    Time-Periodic Optical Activity

    , 2024 Eighteenth International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials), Publisher: IEEE, Pages: 1-3
  • Conference paper
    De Corte A, Koufidis SF, McCall MW, Maes Bet al., 2024,

    Exceptional Points of Degeneracy in Coupled Chirowaveguides

    , 2024 Eighteenth International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials), Publisher: IEEE, Pages: 1-3
  • Journal article
    Lerendegui M, Riemer K, Papageorgiou G, Wang B, Lachlan A, Chavignon A, Zhang T, Couture O, Huang P, Ashikuzzaman M, Dencks S, Dunsby C, Helfield B, Jensen ØA, Lisson T, Lowerison MR, Rivaz H, Samir AE, Schmitz G, Schoen S, Ruud VS, Pengfei S, Stevens T, Yan J, Sboros V, Tang Met al., 2024,

    ULTRA-SR challenge: assessment of UltrasoundLocalization and TRacking algorithms for super-resolution imaging

    , IEEE Transactions on Medical Imaging, Vol: 43, Pages: 2970-2987, ISSN: 0278-0062

    With the widespread interest and uptake of super-resolution ultrasound (SRUS) through localization and tracking of microbubbles, also known as ultrasound localization microscopy (ULM), many localization and tracking algorithms have been developed. ULM can image many centimeters into tissue in-vivo and track microvascular flow non-invasively with sub-diffraction resolution. In a significant community effort, we organized a challenge, Ultrasound Localization and TRacking Algorithms for Super-Resolution (ULTRA-SR). The aims of this paper are threefold: to describe the challenge organization, data generation, and winning algorithms; to present the metrics and methods for evaluating challenge entrants; and to report results and findings of the evaluation. Realistic ultrasound datasets containing microvascular flow for different clinical ultrasound frequencies were simulated, using vascular flow physics, acoustic field simulation and nonlinear bubble dynamics simulation. Based on these datasets, 38 submissions from 24 research groups were evaluated against ground truth using an evaluation framework with six metrics, three for localization and three for tracking. In-vivo mouse brain and human lymph node data were also provided, and performance assessed by an expert panel. Winning algorithms are described and discussed. The publicly available data with ground truth and the defined metrics for both localization and tracking present a valuable resource for researchers to benchmark algorithms and software, identify optimized methods/software for their data, and provide insight into the current limits of the field. In conclusion, Ultra-SR challenge has provided benchmarking data and tools as well as direct comparison and insights for a number of the state-of-the art localization and tracking algorithms.
  • Journal article
    Hansen-Shearer J, Yan J, Lerendegui M, Huang B, Toulemonde M, Riemer K, Tan Q, Tonko J, Weinberg PD, Dunsby C, Tang M-Xet al., 2024,

    Ultrafast 3-D Transcutaneous Super Resolution Ultrasound Using Row-Column Array Specific Coherence-Based Beamforming and Rolling Acoustic Sub-aperture Processing: In Vitro, in Rabbit and in Human Study

    , ULTRASOUND IN MEDICINE AND BIOLOGY, Vol: 50, Pages: 1045-1057, ISSN: 0301-5629
  • Journal article
    Darling C, Kumar S, Alexandrov Y, de Faye J, Almagro Santiago J, Rýdlová A, Bugeon L, Dallman MJ, Behrens AJ, French PMW, McGinty Jet al., 2024,

    Optical projection tomography implemented for accessibility and low cost (OPTImAL)

    , Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, Vol: 382, ISSN: 1364-503X

    Optical projection tomography (OPT) is a three-dimensional mesoscopic imaging modality that can use absorption or fluorescence contrast, and is widely applied to fixed and live samples in the mm-cm scale. For fluorescence OPT, we present OPT implemented for accessibility and low cost, an open-source research-grade implementation of modular OPT hardware and software that has been designed to be widely accessible by using low-cost components, including light-emitting diode (LED) excitation and cooled complementary metal-oxide-semiconductor (CMOS) cameras. Both the hardware and software are modular and flexible in their implementation, enabling rapid switching between sample size scales and supporting compressive sensing to reconstruct images from undersampled sparse OPT data, e.g. to facilitate rapid imaging with low photobleaching/phototoxicity. We also explore a simple implementation of focal scanning OPT to achieve higher resolution, which entails the use of a fan-beam geometry reconstruction method to account for variation in magnification. This article is part of the Theo Murphy meeting issue 'Open, reproducible hardware for microscopy'.
  • Journal article
    Lerendegui M, Yan J, Stride E, Dunsby C, Tang M-Xet al., 2024,

    Understanding the effects of microbubble concentration on localization accuracy in super-resolution ultrasound imaging

    , PHYSICS IN MEDICINE AND BIOLOGY, Vol: 69, ISSN: 0031-9155
  • Journal article
    Dent LG, Curry N, Sparks H, Bousgouni V, Maioli V, Kumar S, Munro I, Butera F, Jones I, Arias-Garcia M, Rowe-Brown L, Dunsby C, Bakal Cet al., 2024,

    Environmentally dependent and independent control of 3D cell shape

    , CELL REPORTS, Vol: 43, ISSN: 2211-1247
  • Journal article
    Riemer K, Tan Q, Morse S, Bau L, Toulemonde M, Yan J, Zhu J, Wang B, Taylor L, Lerendegui M, Wu Q, Stride E, Dunsby C, Weinberg PD, Tang M-Xet al., 2024,

    3D Acoustic Wave Sparsely Activated Localization Microscopy With Phase Change Contrast Agents

    , INVESTIGATIVE RADIOLOGY, Vol: 59, Pages: 379-390, ISSN: 0020-9996
  • Journal article
    Zeng H-J, Xue W-Z, Murray RT, Cui C, Wang L, Pan Z, Loiko P, Mateos X, Yuan F, Zhang G, Griebner U, Petrov V, Chen Wet al., 2024,

    In-band pumped Kerr-lens mode-locked Tm,Ho-codoped calcium aluminate laser

    , OPTICS EXPRESS, Vol: 32, Pages: 16083-16089, ISSN: 1094-4087
  • Journal article
    Temel T, Murray RT, Wang L, Chen W, Schirrmacher A, Battle RA, Petrov Vet al., 2024,

    Narrowband-seeded PPLN non-resonant optical parametric oscillator

    , OPTICAL MATERIALS EXPRESS, Vol: 14, ISSN: 2159-3930
  • Journal article
    Xiao H, Jiang X, Damzen MJ, 2024,

    Transient pump-probe analysis of pump-induced lensing in laser amplifiers

    , Optics Express, Vol: 32, Pages: 12783-12799, ISSN: 1094-4087

    Understanding of pump-induced lensing in laser amplifiers is essential for the optimized design of high-power lasers with high spatial quality, but there is usually incomplete knowledge of the interplay between thermal and population induced lensing mechanisms, lensing under lasing and non-lasing conditions, and transient lensing effects under pulsed operation. This paper provides quantitative insight of pump-induced lensing effects by using experimental transient pump-probe measurements in an alexandrite laser amplifier end-pumped by a short pulse pump beam with Gaussian spatial intensity distribution. Lensing results are presented showing a large difference in lensing under both non-lasing and lasing conditions and distinction of the population lens and thermal lens contributions from their different response time. Different pump beam sizes are used to show the variation of the relative strength of the lensing mechanisms. Comparison of experimental results with the analytical transient theory developed in this paper for the Gaussian pump beam gives excellent agreement and quantitative information on the thermal and population contributions to the amplifier lens. This paper provides a methodology for quantitative investigation of pump-induced lensing in general laser amplifier systems, and potentially other classes of optical materials with residual optical absorption.
  • Conference paper
    Codescu M-A, Murray JM, Zawilski KT, Schunemann PG, Murray RT, Guha Set al., 2024,

    Optical Parametric Generation in Non-Critically Cut CdSiP2 with a Nanosecond 1.064 μm Nd:YAG Laser

    , Optica High-Brightness Sources and Light-Driven Interactions Congress
  • Conference paper
    Murray RT, Battle RA, Simon D, Xiang Y, Robinson K, Azevedo Magalhães SF, Wang Y, Runcorn TH, Takats Zet al., 2024,

    Visualizing metabolites at the cellular level: advancements in 3-micron laser desorption mass spectrometry imaging

    , SPIE BiOS, Publisher: SPIE, Pages: 4-4

    By combining high beam quality picosecond pulsed optical parametric amplifiers at 2.94 μm with Rapid Evap-ortive Ionisation Mass Spectrometry (REIMS), we have demonstrated record spatial pixel resolutions for ambientmass spectrometry (MS) imaging of < 10 μm. In this contribution, we introduce our work in this area, demon-strating the platform workflow and highlighting recent results of metabolic imaging at the single cell resolutionlevel.
  • Journal article
    Temel T, Murray RT, Wang L, Chen W, Schirrmacher A, Divliansky IB, Mhibik O, Glebov LB, Petrov Vet al., 2024,

    Energy scaling of a narrowband, periodically poled LiNbO3, nanosecond, nonresonant optical parametric oscillator

    , APPLIED OPTICS, Vol: 63, Pages: 1811-1814, ISSN: 1559-128X
  • Journal article
    Bharadwaj A, Kalita R, Kumar A, Sarma A, Jaganathan BG, Kumar S, Gorlitz F, Lightley J, Dunsby C, Neil M, Hollick C, Graham J, French PMW, Boruah BRet al., 2024,

    A cost-effective, modular, research-grade optical microscope

    , CURRENT SCIENCE, Vol: 126, Pages: 244-254, ISSN: 0011-3891
  • Conference paper
    Murray JM, Codescu M-A, Zawilski KT, Schunemann PG, Murray R, Guha Set al., 2024,

    Optical Parametric Generation in Non-Critically Cut CdSiP2 with a Nanosecond 1.064 μm Nd:YAG Laser

    , Optica High-Brightness Sources and Light-Driven Interactions Congress
  • Conference paper
    Zeng HJ, Xue WZ, Murray RT, Cui C, Wang L, Pan Z, Loiko P, Mateos X, Zhang G, Griebner U, Petrov V, Chen Wet al., 2024,

    In-Band Pumped Kerr-Lens Mode-Locked Tm,Ho-codoped Calcium Aluminate Laser

    We report on a Kerr-lens mode-locked Tm,Ho,Lu:CaGdAlO4 laser, in-band pumped by a fiber Raman laser at 1678 nm. 79-fs pulses were generated at 2073.6 nm with an average power of 91 mW at 85.7 MHz.
  • Conference paper
    Bottrill KRH, Taengnoi N, Wang Y, Sahu JK, Petropoulos Pet al., 2024,

    1200km Coherent O-band Transmission using In-line BDFAs and Standard Single-mode Fibre

    We demonstrate a record 1200km reach O-band transmission of a 22.5GBd dual-pol QPSK signal using a recirculating loop with in-line BDFA amplification and 50km spans of standard single-mode fibre.
  • Conference paper
    Wang Y, Battle RA, Simon D, Xiang Y, Azevedo Magalhaes SF, Robinson KN, Runcorn TH, Takats Z, Murray RTet al., 2024,

    Laser Ablation of Biological Tissue with a 2.94 μm Picosecond Optical Parametric Amplifier for Ambient Mass Spectrometry Imaging

    We report a 2.94 μm OPA with ∼100 ps pulse duration, 400 nJ pulse energy and a 500 kHz repetition rate, which enables high resolution (≤10 μm) laser desorption-based mass spectrometry imaging of biological tissue.
  • Conference paper
    Bottrill KRH, Taengnoi N, Wang Y, Sahu JK, Petropoulos Pet al., 2024,

    1200km Coherent O-band Transmission using In-line BDFAs and Standard Single-mode Fibre

    We demonstrate a record 1200km reach O-band transmission of a 22.5GBd dual-pol QPSK signal using a recirculating loop with in-line BDFA amplification and 50km spans of standard single-mode fibre.
  • Conference paper
    Runcorn TH, Murray RT, Taylor JR, 2024,

    Multi-watt red nanosecond frequency-doubled Raman-shifted fiber laser

    , Conference on Nonlinear Frequency Generation and Conversion - Materials and Devices XXIII, Publisher: SPIE-INT SOC OPTICAL ENGINEERING, ISSN: 0277-786X
  • Conference paper
    Krawczyk B, Kudlinski A, Battle RA, Murray RT, Runcorn THet al., 2024,

    Enhancement of four-wave mixing via stimulated emission in a Yb-doped photonic crystal fiber

    , Conference on Fiber Lasers XXI - Technology and Systems, Publisher: SPIE-INT SOC OPTICAL ENGINEERING, ISSN: 0277-786X
  • Journal article
    Paie P, Calisesi G, Candeo A, Comi A, Sala F, Ceccarelli F, De Luigi A, Veglianese P, Muhlberger K, Fokine M, Valentini G, Osellame R, Neil M, Bassi A, Bragheri Fet al., 2023,

    Structured-light-sheet imaging in an integrated optofluidic platform

    , LAB ON A CHIP, Vol: 24, Pages: 34-46, ISSN: 1473-0197

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