See a list of publications below or visit the Photonics academic staff page and click on a particular  member of staff to access their personal web page, which includes a list of their own publications.

Search or filter publications

Filter by type:

Filter by publication type

Filter by year:

to

Results

  • Showing results for:
  • Reset all filters

Search results

  • 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, Pages: 889-889

    <jats:p>A PPLN non-resonant optical parametric oscillator injection-seeded by narrowband sub-100-mW CW radiation at the signal wavelength produces &gt; 3 W idler average power at 2376 nm for a 20-kHz repetition rate, with a sub-2-nm spectral linewidth. The maximum quantum efficiency reaches 39.5%, roughly 1.4 times higher compared to narrowband operation achieved with a volume Bragg grating at the same pump level. Seed levels as low as 40 mW are sufficient to produce the desired spectral narrowing effect.</jats:p>

  • 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 LiNbO<sub>3</sub>, nanosecond, nonresonant optical parametric oscillator

    , Applied Optics, Vol: 63, Pages: 1811-1811, ISSN: 1559-128X

    <jats:p>We demonstrate that 3-mm-thick, periodically poled LiNbO<jats:sub>3</jats:sub> enables energy scaling of a nonresonant optical parametric oscillator operated in the narrowband mode with a volume Bragg grating at the signal wavelength. Utilizing the full available pump power at 1064 nm, we obtained maximum average powers of 2.25 and 2.08 W for the signal (1.922 µm) and idler (2.383 µm) pulses at 10 kHz, at a total conversion efficiency of 32.8%, which represents a fourfold increase in terms of peak powers over our previous work. The signal and idler spectral linewidths were ∼1nm, with pulse lengths of ∼6ns and an idler beam propagation factor of ∼5.</jats:p>

  • 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: 244-2554, ISSN: 0011-3891

    Optical microscopy is a ubiquitous tool in the physical and life sciences and in histopathology, where visible light microscopy is used to analyse clinical tissue sections at the micron scale to help diagnose diseases. In recent years, microscope technologies have dramatically evolved, but these have generally come with increased cost and complexity. To widen access to advanced microscopy capabilities, we have developed a cost-effective modular platform for optical microscopy (www.openscopes.com). Many of these instruments can be based around a new low-cost and flexible microscope stand, ‘openFrame’, for which the core components are open source. openFrame can support implementations of a wide range of microscope modalities for diverse applications, including research, pathology and training. Unlike many commercial microscopes that are often designed for specific applications and cannot be easily upgraded or adapted for different imaging modalities, openFramebased instruments can be relatively easily maintained, upgraded or adapted to another modality without requiring manufacturer support. To this end, openFramebased instruments are envisaged to operate with opensource software, enabling researchers to assemble and modify their microscopes with minimal challenges presented by proprietary (closed) hardware or software. Here, we describe the implementation of a low-cost, research-grade modular optical microscope applicable to research and pathology.

  • Journal article
    Paiè 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 Chip, Vol: 24, Pages: 34-46

    Heterogeneity investigation at the single-cell level reveals morphological and phenotypic characteristics in cell populations. In clinical research, heterogeneity has important implications in the correct detection and interpretation of prognostic markers and in the analysis of patient-derived material. Among single-cell analysis, imaging flow cytometry allows combining information retrieved by single cell images with the throughput of fluidic platforms. Nevertheless, these techniques might fail in a comprehensive heterogeneity evaluation because of limited image resolution and bidimensional analysis. Light sheet fluorescence microscopy opened new ways to study in 3D the complexity of cellular functionality in samples ranging from single-cells to micro-tissues, with remarkably fast acquisition and low photo-toxicity. In addition, structured illumination microscopy has been applied to single-cell studies enhancing the resolution of imaging beyond the conventional diffraction limit. The combination of these techniques in a microfluidic environment, which permits automatic sample delivery and translation, would allow exhaustive investigation of cellular heterogeneity with high throughput image acquisition at high resolution. Here we propose an integrated optofluidic platform capable of performing structured light sheet imaging flow cytometry (SLS-IFC). The system encompasses a multicolor directional coupler equipped with a thermo-optic phase shifter, cylindrical lenses and a microfluidic network to generate and shift a patterned light sheet within a microchannel. The absence of moving parts allows a stable alignment and an automated fluorescence signal acquisition during the sample flow. The platform enables 3D imaging of an entire cell in about 1 s with a resolution enhancement capable of revealing sub-cellular features and sub-diffraction limit details.

  • Journal article
    Liang M, Minassian A, Damzen MJ, 2023,

    High-energy acousto-optic Q-switched alexandrite laser with wavelength tunable fundamental and UV second harmonic generation

    , Optics Express, Vol: 31, Pages: 42428-42438, ISSN: 1094-4087

    We investigate high-energy mJ-class diode-pumped acousto-optic (AO) Q-switched alexandrite lasers with broad tunability at both the fundamental near-IR wavelength range and second harmonic generation (SHG) in the UV wavelength range. An AO Q-switched alexandrite laser with continuous-wave diode-pumping has been operated at up to 10 kHz and producing pulse energy of 700 µJ at repetition rate of 1 kHz. With pulsed double-pass diode-pumping, we demonstrate higher pulse energy of 2.6 mJ. With wavelength tuning, this laser system demonstrated broad fundamental tuning range from 719 to 787 nm with diffraction-limited beam quality (M2 = 1.05). By external cavity second harmonic generation in a Type-I LBO crystal, pulse energy of 0.66 mJ is generated at 375 nm and with UV tuning range from 361 to 391 nm. To our knowledge, this is the first demonstration of AO Q-switched alexandrite laser with broad wavelength tuning in the near-IR and UV wavelength ranges and shows its excellent potential as a pulsed source for future applications.

  • Journal article
    Zeng H, Xue W, Murray RT, Chen W, Pan Z, Wang L, Cui C, Loiko P, Mateos X, Griebner U, Petrov Vet al., 2023,

    Continuous-Wave and Mode-Locked Operation of an In-Band Pumped Tm,Ho,Lu:CaGdAlO4 Laser

    , Applied Sciences, Vol: 13, Pages: 12927-12927

    <jats:p>We investigate in-band pumping of a Tm,Ho,Lu:CaGdAlO4 laser using a Raman-shifted Er-fiber laser (1678 nm), in the continuous-wave (CW) and mode-locked (ML) regimes. A maximum output power of 524 mW is obtained in the CW regime with a 5% output coupler at an absorbed pump power of 2.04 W, corresponding to a slope efficiency of 27.9%. A maximum CW wavelength tuning range of 160 nm at the zero level, from 1984 to 2144 nm, is obtained with a 0.2% output coupler. In the ML regime, pumping with 5.5 W (unpolarized), the average output power (0.2% output coupler) reaches 148 mW at a repetition rate of ~96 MHz. The output spectrum is centered at 2071.5 nm with a FWHM of 21.5 nm (σ-polarization). The pulse duration amounts to 218 fs (time-bandwidth product equal to 0.327).</jats:p>

  • Journal article
    Ahmad H, Roslan NA, Zaini MKA, Samion MZ, Reduan SA, Wang Y, Wang S, Sahu JK, Yasin Met al., 2023,

    Generation of multiwavelength bismuth-doped fiber laser based on all-fiber Lyot filter

    , Optical Fiber Technology, Vol: 81, ISSN: 1068-5200

    A stable multiwavelength fiber laser was proposed and demonstrated using a bismuth-doped fiber together with an all-fiber Lyot filter. The proposed multiwavelength bismuth-doped fiber laser (BDFL) spectrum can generate up to 21 output channels between 1309.88 nm and 1313.69 nm by carefully adjusting two polarization controllers (PCs). The multiwavelength BDFL shows good stability over time with a signal-to-noise ratio (SNR) of 48.69 dB, contributing to the average power fluctuations of 0.6 dB and wavelength drift of less than 0.1 nm in the laser output. In addition, the multiwavelength BDFL exhibits a free spectral range (FSR) of about 0.192 nm and a frequency bandwidth of 33.45 GHz. The characteristics of the multiwavelength BDFL can be observed by varying the pump power of the pump source, lasing output at different lengths of polarization maintaining fiber (PMF), and the generation in multiwavelengths using additional single mode-fiber (SMF).

  • 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., 2023,

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

    , Invest Radiol

    OBJECTIVE: The aim of this study is to demonstrate 3-dimensional (3D) acoustic wave sparsely activated localization microscopy (AWSALM) of microvascular flow in vivo using phase change contrast agents (PCCAs). MATERIALS AND METHODS: Three-dimensional AWSALM using acoustically activable PCCAs was evaluated on a crossed tube microflow phantom, the kidney of New Zealand White rabbits, and the brain of C57BL/6J mice through intact skull. A mixture of C 3 F 8 and C 4 F 10 low-boiling-point fluorocarbon gas was used to generate PCCAs with an appropriate activation pressure. A multiplexed 8-MHz matrix array connected to a 256-channel ultrasound research platform was used for transmitting activation and imaging ultrasound pulses and recording echoes. The in vitro and in vivo echo data were subsequently beamformed and processed using a set of customized algorithms for generating 3D super-resolution ultrasound images through localizing and tracking activated contrast agents. RESULTS: With 3D AWSALM, the acoustic activation of PCCAs can be controlled both spatially and temporally, enabling contrast on demand and capable of revealing 3D microvascular connectivity. The spatial resolution of the 3D AWSALM images measured using Fourier shell correlation is 64 μm, presenting a 9-time improvement compared with the point spread function and 1.5 times compared with half the wavelength. Compared with the microbubble-based approach, more signals were localized in the microvasculature at similar concentrations while retaining sparsity and longer tracks in larger vessels. Transcranial imaging was demonstrated as a proof of principle of PCCA activation in the mouse brain with 3D AWSALM. CONCLUSIONS: Three-dimensional AWSALM generates volumetric ultrasound super-resolution microvascular images in vivo with spatiotemporal selectivity and enhanced microvascular penetration.

  • Journal article
    Koufidis SF, McCall MW, 2023,

    Wavelength-independent Bragg-like reflection in uniaxial bi-anisotropic media

    , Journal of the Optical Society of America B, Vol: 40, Pages: 2829-2829, ISSN: 0740-3224

    <jats:p>We have recently shown that a uniform birefringent medium exhibits a circular Bragg phenomenon that relies solely on resonant tuning of the medium’s parameters, rather than on a particular wavelength resonance, thus rendering its electromagnetic response arbitrarily broadband. The resonant condition, however, necessitated a chirality parameter equal to the average refractive index. Here, we demonstrate that non-axial wave propagation in an axially bi-anisotropic uniaxial medium also enacts such a response and, moreover, relaxes the severity of the tuning condition, offering a convenient platform for controlling both the location of the resonance and the corresponding bandwidth. Anomalous wave propagation at a singular point is additionally identified, in the vicinity of which a remarkably high and intrinsically broadband refractive index can be realized. Recent demonstrations of meta-media with giant and controllable chirality pave the path towards the realistic embodiment of a highly efficient optical modulator.</jats:p>

  • Journal article
    Hong W, Sparks H, Dunsby C, 2023,

    Alignment and characterisation of remote-refocusingsystems

    , Applied Optics, Vol: 62, Pages: 7431-7440, ISSN: 1559-128X

    The technique of remote refocusing is used in optical microscopy to provide rapid axial scanning without mechanically perturbing the sample and in techniques such as oblique plane microscopy that build on remote refocusing to image a tilted plane within the sample. The magnification between the pupils of the primary (O1) and secondary (O2) microscope objectives of the remote-refocusing system has been shown previously by Mohanan and Corbett [J. Microsc. 288, 95 (2022) [CrossRef] ] to be crucial in obtaining the broadest possible remote-refocusing range. In this work, we performed an initial alignment of a remote-refocusing system and then studied the effect of axial misalignments of O1 and O2, axial misalignment of the primary tube lens (TL1) relative to the secondary tube lens (TL2), lateral misalignments of TL2, and changes in the focal length of TL2. For each instance of the setup, we measured the mean point spread function FWHMxy of 100 nm fluorescent beads and the normalized bead integrated fluorescence signal, and we calculated the axial and lateral distortion of the system; all of these quantities were mapped over the remote-refocusing range and as a function of lateral image position. This allowed us to estimate the volume over which diffraction-limited performance is achieved and how this changes with the alignment of the system.

  • Journal article
    Lightley J, Kumar S, Lim MQ, Garcia E, Goerlitz F, Alexandrov Y, Parrado T, Hollick C, Steele E, Rossmann K, Graham J, Broichhagen J, Mcneish IA, Roufosse CA, Neil MAA, Dunsby C, French PMWet al., 2023,

    <i>openFrame</i>: A modular, sustainable, open microscopy platform with single-shot, dual-axis optical autofocus module providing high precision and long range of operation

    , JOURNAL OF MICROSCOPY, ISSN: 0022-2720
  • Journal article
    Koufidis SF, Koutserimpas TT, McCall MW, 2023,

    Temporal analog of Bragg gratings

    , Optics Letters, Vol: 48, Pages: 4500-4500, ISSN: 0146-9592

    <jats:p>Recently, scalar coupled-wave theory has been employed to analyze a medium with periodic time-varying permittivity, providing simple expressions and, consequently, straightforward insights into the parametric amplification mechanism. Here, we combine such an approach with the Möbius transformation method to investigate the dispersion and optical response of a finite “time-slab” of the aforementioned medium. We demonstrate the temporal analog of a Bragg grating, discuss the differences with its spatial counterpart, and examine nontrivial scenarios of the permittivity’s time-modulation, such as chirping and apodization. Furthermore, we propose a highly selective and, moreover, single-spatial-interface optical sensor, based on phase delineation.</jats:p>

  • Journal article
    Tawy G, Davidson NP, Churchill G, Damzen MJ, Smith PGR, Gates JC, Gawith CBEet al., 2023,

    Temperature-tunable UV generation using an Alexandrite laser and PPLN waveguides

    , OPTICS EXPRESS, Vol: 31, Pages: 22757-22765, ISSN: 1094-4087
  • Journal article
    Taylor JR, 2023,

    Early optical soliton research at Imperial College London

    , OPTICS COMMUNICATIONS, Vol: 536, ISSN: 0030-4018
  • Journal article
    Smith M, Sparks H, Almagro J, Chaigne A, Behrens A, Dunsby C, Salbreux Get al., 2023,

    Active mesh and neural network pipeline for cell aggregate segmentation

    , Biophysical Journal, Vol: 122, Pages: 1586-1599, ISSN: 0006-3495

    Segmenting cells within cellular aggregates in 3D is a growing challenge in cell biology due to improvements in capacity and accuracy of microscopy techniques. Here, we describe a pipeline to segment images of cell aggregates in 3D. The pipeline combines neural network segmentations with active meshes. We apply our segmentation method to cultured mouse mammary gland organoids imaged over 24 h with oblique plane microscopy, a high-throughput light-sheet fluorescence microscopy technique. We show that our method can also be applied to images of mouse embryonic stem cells imaged with a spinning disc microscope. We segment individual cells based on nuclei and cell membrane fluorescent markers, and track cells over time. We describe metrics to quantify the quality of the automated segmentation. Our segmentation pipeline involves a Fiji plugin that implements active mesh deformation and allows a user to create training data, automatically obtain segmentation meshes from original image data or neural network prediction, and manually curate segmentation data to identify and correct mistakes. Our active meshes-based approach facilitates segmentation postprocessing, correction, and integration with neural network prediction.

  • Journal article
    Riemer K, Toulemonde M, Yan J, Lerendegui M, Stride E, Weinberg PD, Dunsby C, Tang M-Xet al., 2023,

    Fast and selective super-resolution ultrasound in vivo with acoustically activated nanodroplets

    , IEEE Transactions on Medical Imaging, Vol: 42, Pages: 1056-1067, ISSN: 0278-0062

    Perfusion by the microcirculation is key to the development, maintenance and pathology of tissue. Its measurement with high spatiotemporal resolution is consequently valuable but remains a challenge in deep tissue. Ultrasound Localization Microscopy (ULM) provides very high spatiotemporal resolution but the use of microbubbles requires low contrast agent concentrations, a long acquisition time, and gives little control over the spatial and temporal distribution of the microbubbles. The present study is the first to demonstrate Acoustic Wave Sparsely-Activated Localization Microscopy (AWSALM) and fast-AWSALM for in vivo super-resolution ultrasound imaging, offering contrast on demand and vascular selectivity. Three different formulations of acoustically activatable contrast agents were used. We demonstrate their use with ultrasound mechanical indices well within recommended safety limits to enable fast on-demand sparse activation and destruction at very high agent concentrations. We produce super-localization maps of the rabbit renal vasculature with acquisition times between 5.5 s and 0.25 s, and a 4-fold improvement in spatial resolution. We present the unique selectivity of AWSALM in visualizing specific vascular branches and downstream microvasculature, and we show super-localized kidney structures in systole (0.25 s) and diastole (0.25 s) with fast-AWSALM outdoing microbubble based ULM. In conclusion, we demonstrate the feasibility of fast and selective measurement of microvascular dynamics in vivo with subwavelength resolution using ultrasound and acoustically activatable nanodroplet contrast agents.

  • Conference paper
    Hong Y, Taengnoi N, Bottrill KRH, Wang Y, Sahu JK, Petropoulos P, Richardson DJet al., 2023,

    Experimental investigation of BDFA-based O-band direct-detection transmission using an optical recirculating loop.

    , Pages: 10978-10990

    We implemented a bismuth-doped fiber amplifier (BDFA) based optical recirculating loop to investigate the performance of amplified O-band transmission over appreciable distances. Both single-wavelength and wavelength-division multiplexed (WDM) transmission were studied, with a variety of direct-detection modulation formats. We report on (a) transmission over lengths of up to 550 km in a single-channel 50-Gb/s system operating at wavelengths ranging from 1325 nm to 1350 nm, and (b) rate-reach products up to 57.6 Tb/s-km (after accounting for the forward error correction redundancy) in a 3-channel system.

  • Journal article
    Gleneadie HJJ, Fernandez-Ruiz B, Sardini A, Van de Pette M, Dimond A, Prinjha RKK, McGinty J, French PMW, Bagci H, Merkenschlager M, Fisher AGGet al., 2023,

    Endogenous bioluminescent reporters reveal a sustained increase in utrophin gene expression upon EZH2 and ERK1/2 inhibition

    , COMMUNICATIONS BIOLOGY, Vol: 6
  • Journal article
    McCall MW, Koufidis SF, 2023,

    Broadband Bragg phenomenon in a uniform birefringent medium

    , OPTICS LETTERS, Vol: 48, Pages: 1096-1099, ISSN: 0146-9592
  • Journal article
    Tawy G, Minassian A, Damzen MJ, 2023,

    Power-scaled CW Alexandrite lasers

    , APPLIED PHYSICS B-LASERS AND OPTICS, Vol: 129, ISSN: 0946-2171
  • Journal article
    Dvinskikh L, Sparks H, Brito L, MacLeod K, Harding S, Dunsby Cet al., 2023,

    Remote-refocusing light-sheet fluorescence microscopy enables 3D imaging of electromechanical coupling of hiPSC-derived and adult cardiomyocytes in co-culture

    , Scientific Reports, Vol: 13, Pages: 1-14, ISSN: 2045-2322

    Improving cardiac function through stem-cell regenerative therapy requires functional and structural integration of the transplanted cells with the host tissue. Visualizing the electromechanical interaction between native and graft cells necessitates 3D imaging with high spatio-temporal resolution and low photo-toxicity. A custom light-sheet fluorescence microscope was used for volumetric imaging of calcium dynamics in co-cultures of adult rat left ventricle cardiomyocytes and human induced pluripotent stem cell-derived cardiomyocytes. Aberration-free remote refocus of the detection plane synchronously to the scanning of the light sheet along the detection axis enabled fast dual-channel 3D imaging at subcellular resolution without mechanical sample disturbance at up to 8 Hz over a ∼300 µm × 40 µm × 50 µm volume. The two cell types were found to undergo electrically stimulated and spontaneous synchronized calcium transients and contraction. Electromechanical coupling improved with co-culture duration, with 50% of adult-CM coupled after 24 h of co-culture, compared to 19% after 4 h (p = 0.0305). Immobilization with para-nitroblebbistatin did not prevent calcium transient synchronization, with 35% and 36% adult-CM coupled in control and treated samples respectively (p = 0.91), indicating that electrical coupling can be maintained independently of mechanotransduction.

  • Journal article
    Dvinskikh L, Sparks H, MacLeod K, Dunsby Cet al., 2023,

    High-speed 2D light-sheet fluorescence microscopy enables quantification of spatially varying calcium dynamics in ventricular cardiomyocytes

    , Frontiers in Physiology, Vol: 14, Pages: 1-14, ISSN: 1664-042X

    Introduction: Reduced synchrony of calcium release and t-tubule structure organization in individual cardiomyocytes has been linked to loss of contractile strength and arrhythmia. Compared to confocal scanning techniques widely used for imaging calcium dynamics in cardiac muscle cells, light-sheet fluorescence microscopy enables fast acquisition of a 2D plane in the sample with low phototoxicity.Methods: A custom light-sheet fluorescence microscope was used to achieve dual-channel 2D timelapse imaging of calcium and the sarcolemma, enabling calcium sparks and transients in left and right ventricle cardiomyocytes to be correlated with the cell microstructure. Imaging electrically stimulated dual-labelled cardiomyocytes immobilized with para-nitroblebbistatin, a non-phototoxic, low fluorescence contraction uncoupler, with sub-micron resolution at 395 fps over a 38 μm × 170 µm FOV allowed characterization of calcium spark morphology and 2D mapping of the calcium transient time-to-half-maximum across the cell.Results: Blinded analysis of the data revealed sparks with greater amplitude in left ventricle myocytes. The time for the calcium transient to reach half-maximum amplitude in the central part of the cell was found to be, on average, 2 ms shorter than at the cell ends. Sparks co-localized with t-tubules were found to have significantly longer duration, larger area and spark mass than those further away from t-tubules.Conclusion: The high spatiotemporal resolution of the microscope and automated image-analysis enabled detailed 2D mapping and quantification of calcium dynamics of n = 60 myocytes, with the findings demonstrating multi-level spatial variation of calcium dynamics across the cell, supporting the dependence of synchrony and characteristics of calcium release on the underlying t-tubule structure.

  • Journal article
    Damzen M, Xiao H, Jiang X, 2023,

    Alexandrite lasers with blue-diode-pumping

    , Optics Express, Vol: 31, Pages: 5832-5842, ISSN: 1094-4087

    The availability of high-power and high-brightness blue diode lasers makes them attractive as low-cost pump sources for broadly tunable Alexandrite lasers. In this paper we investigate the performance of an Alexandrite laser pumped by a high-power fiber-delivered blue diode module. Output power 1.84 W is achieved, the highest power from blue diode pumped Alexandrite to date. Excellent pump absorption is demonstrated of scrambled pump polarization on both a-axis and b-axis of Alexandrite crystal. Wavelength tuning and dual wavelength operation is produced using the self-birefringent filtering of the Brewster-cut Alexandrite crystal. An analysis is made of laser efficiency and mode formation including the creation of higher-order Laguerre-Gaussian vortex modes (LG01 and LG02). Performance is compared to red diode pumping and prospects for further optimization and power-scaling are discussed.

  • Journal article
    Wang Y, Wang S, Halder A, Sahu Jet al., 2023,

    (INVITED) Bi-doped optical fibers and fiber amplifiers

    , Optical Materials: X, Vol: 17

    Bismuth (Bi)-doped aluminosilicate, phosphosilicate, germanosilicate and high (⩾50 mol%) germanosilicate fibers have shown luminescence around 1.15 μm, 1.3 μm, 1.45 μm and 1.7 μm, respectively. Bi-doped fibers have paved the way for developing optical amplifiers and fiber lasers in the wavelength region of 1150–1500 nm and 1600–1700 nm, where it can serve a wide range of applications in astronomy, imaging, medicine and advanced optical communications. However, spectroscopic study is required to understand the nature of near-infrared (NIR)-emitting Bi active centers (BACs) to improve the efficiency of Bi-doped fiber amplifiers and lasers. In this paper, we review the luminescence properties of Bi-doped glasses as well as Bi-doped fibers with aluminosilicate, phosphosilicate, and germanosilicate glass hosts. Absorption and emission cross-sections of Bi-doped phosphosilicate fibers are reported. In addition, we review the current state of the art of Bi-doped fiber amplifiers development in the second telecom window (O-band) and in the E-band and S-band for the next-generation high-capacity optical communications.

  • Journal article
    Darling C, Davis SPX, Kumar S, French PMW, McGinty Jet al., 2023,

    Single-shot optical projection tomography for high-speed volumetric imaging of dynamic biological samples

    , JOURNAL OF BIOPHOTONICS, Vol: 16, ISSN: 1864-063X
  • Journal article
    Taylor JR, 2023,

    Fiber Laser Driven Three-Micron Source Development Based on Difference Frequency Generation

    , OPTOELECTRONICS INSTRUMENTATION AND DATA PROCESSING, Vol: 59, Pages: 18-27, ISSN: 8756-6990
  • Journal article
    Battle RA, Chandran AM, Runcorn TH, Mussot A, Kudlinski A, Murray RT, Taylor JRet al., 2023,

    Mid-infrared difference-frequency generation directly pumped by a fiber four-wave mixing source

    , OPTICS LETTERS, Vol: 48, Pages: 387-390, ISSN: 0146-9592
  • Conference paper
    Geberbauer JWT, Murray RT, Runcorn TH, Kerridge-Johns WRet al., 2023,

    Yb fiber vortex laser using an interferometric mode converting output coupler

    , ISSN: 0277-786X

    We apply mode transformation to an Yb fiber laser for direct generation of a first order vortex mode (LG01), yielding LG01 power of 5 W at 96 % purity (from modal decomposition) with 16 W pumping. The laser used standard single mode Yb doped fibers operating at 1064 nm. A free-space Sagnac interferometer formed one reflector of the cavity by feeding back the internal Gaussian mode of the fiber laser and output coupling a LG01 via interferometric mode transformation. It was stable over hours of operation and days of inactivity, and was insensitive to polarisation. The maximum output power was only limited through heating of a optical element, which could be mitigated with thermal management. We also show that additional spiral phase plates (SPPs) are a route to higher purity, higher order vortex modes than with SPPs alone due to improved intensity matching between LG01 and higher order states.

  • Conference paper
    Wang Y, Halder A, Richardson DJ, Sahu JKet al., 2023,

    A highly temperature-insensitive Bi-doped fiber amplifier in the E+S-band with 20 dB flat gain from 1435-1475 nm

    We report a bismuth-doped fiber amplifier operating in the E+S-band providing a 20.5±1dB flat gain with 5.5±2dB NF from 1435-1475nm for -10dBm input signal. The gain coefficient and temperature-dependent-gain coefficient are 0.065dB/mW and -0.005±0.001dB/, respectively.

  • Conference paper
    Battle RA, Simon D, Xiang Y, Robinson K, Runcorn TH, Murray RT, Taylor JR, Takats Zet al., 2023,

    High resolution mass spectrometry imaging using 3 micron laser ablation

    , ISSN: 1605-7422

    We report a single-cell level resolution (≤10 µm), laser desorption-based mass spectrometry imaging platform. An optical parametric amplifier is used to generate ∼100 ps, 200 nJ pulses at around 3 µm with a maximum repetition rate of 500 kHz. The pulses are tightly focussed on to fresh frozen animal tissue samples with a thickness of 10 µm. Small volumes of tissue are readily ablated by the laser and are subsequently chemically analyzed using a Rapid Evaporative Ionization Mass Spectrometry (REIMS) source installed on a time of flight mass analyzer. Raster scanning the samples through the laser focus enables the acquisition of mass spectrometry data which can be processed into images with pixel size 10 µm without oversampling, corresponding to cellular level resolution.

This data is extracted from the Web of Science and reproduced under a licence from Thomson Reuters. You may not copy or re-distribute this data in whole or in part without the written consent of the Science business of Thomson Reuters.

Request URL: http://www.imperial.ac.uk:80/respub/WEB-INF/jsp/search-t4-html.jsp Request URI: /respub/WEB-INF/jsp/search-t4-html.jsp Query String: id=211&limit=30&resgrpMemberPubs=true&respub-action=search.html Current Millis: 1710819263696 Current Time: Tue Mar 19 03:34:23 GMT 2024