Publications
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.
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Conference paperWang Y, Thipparapu NK, Umnikov AA, et al., 2019,
Temperature dependent gain and noise figure characteristics of O-band bismuth-doped fibre amplifier
We report an O-band BDFA gain and NF performance over the temperature-range of -40 to +60oC. A 34dB gain with 5.5dB NF was obtained at 1340nm in a double-pass-BDFA operating at -40oC. The temperature-dependent-gain was decreased by <0.1dB/oC for temperatures above -20oC across 1310-1360nm wavelength-band.
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Conference paperHong Y, Taengnoi N, Bottrill KRH, et al., 2019,
Dual O+C-band WDM transmission over 1-km hollow core NaNf using an O-band bismuth-doped fibre amplifier
Amplified transmission of WDM channels over the O- and C-bands is demonstrated using a bismuth-doped fibre amplifier. The transmission medium is an ultra-wide bandwidth nested antiresonant fibre (NANF) offering uniform loss performance across all wavelengths of interest. Comparable performance is obtained across the two bands.
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Conference paperWang Y, Thipparapu NK, Wang S, et al., 2019,
O-band bismuth-doped fiber amplifier and its temperature dependent performance
, ISSN: 0277-786XWe report temperature-dependent gain and NF of single-pass and double-pass O-band BDFA from -60 to +80℃. A maximum gain of 41dB, NF 3.8dB was achieved at -60℃ for -23dBm input-signal. The temperature-dependent-gain coefficient was -0.04dB/℃.
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Conference paperQuicke P, Howe CL, Song P, et al., 2019,
Calculation of high numerical aperture lightfield microscope point spread functions
3D deconvolution of lightfield images enables high resolution reconstruction of sample volumes. Previous point spread function calculations assume low to moderate NA objectives. Here we present a simple vectorial calculation valid for high NA objectives.
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Conference paperTawy G, Damzen MJ, 2019,
Tunable and dual wavelength alexandrite laser using the crystal birefringence
Red-diode-pumped Alexandrite lasers has proven to be an efficient method of generating light in the near infrared with broad tunability from 714 to 818 nm recently demonstrated [1]. Conventionally, tunable Alexandrite lasers have used wavelength selective elements such as birefringent filters or external gratings [1, 2]. In this work wavelength tuning is obtained by exploiting the birefringence of the crystal to use the crystal itself as the wavelength selective element, greatly simplifying the cavity and reducing innecessary loss components.
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Conference paperTawy G, Wang J, Damzen MJ, 2019,
Population lensing in alexandrite lasers
Alexandrite (Cr3+:BeAl2O4) is a vibronic laser at 701-858 nm. Its excellent thermo-mechanical properties and high energy storage make it an ideal high power and high energy Q-switched source with recent development in mJ-level red-diode-pumped Alexandrite oscillators and amplifiers [1-3]. Further power scaling of these systems is limited by thermal lensing which has yet to be addressed in great detail. In this work we present experimental and finite element analysis (FEA) results on the investigation of thermal lensing in a red-diode-pumped Alexandrite laser. Differences in the thermal lensing power for non-lasing and lasing conditions are attributed to a 'population lens' effect. In a separate study stable self-Q-switching (SQS) is observed in an Alexandrite laser cavity containing only the gain medium where the SQS loss mechanism is attributed to the population lens.
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Conference paperSathian J, Lian W, Minassian A, et al., 2019,
Brightness-enhanced solid-state light sources: From kaleidoscope effect to uniform illumination
Luminescent concentrators (LCs) are systems that can increase the brightness of lambertian light sources such as an LED. Applications considered for LED-pumped LCs include laser pumping, general lighting and medical illumination [1-3]. Most studies consider the output power, spectrum and efficiency of the LC system. Here we explore the spatial nature of the output of the LCs under both laser and LED illumination.
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Conference paperSathian J, Minassian A, Alford NM, et al., 2019,
Enhancing performance of Ce:YAG luminescent concentrators for high power applications
High power scaling of an LED pumped luminescent concentrator (LC) can address significant excitation and illumination applications, including laser pumping and medical light therapy [1-3]. However, heat deposited into the luminescent material is critical and was already a serious issue in our prior systems [3] where forced air cooling of the Ce:YAG LC light-guide was employed but limited power and/or duration of operation. Here we report the successful demonstration of a temperature controlled Ce:YAG LC pumped with blue InGaN LEDs.
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Conference paperSathian J, Tawy G, Sheng X, et al., 2019,
Compact non-astigmatic alexandrite ring laser with unidirectional single-longitudinal-mode operation
Progress in single frequency and precise wavelength tunable lasers are essential to address future demands in high resolution spectroscopy, metrology and quantum technology systems. Alexandrite lasers with wide tunability in near-IR spectral region when pumped by low cost red diodes provide a good prospect as a cost effective precision laser source. This was demonstrated in our earlier work [1] using a tunable single-frequency bow-tie cavity with Brewster-cut Alexandrite crystal. The astigmatism of the Brewster cut gain medium and need for angled curved mirrors for astigmatic compensation, whilst being well established [2,3] also places some complexity on the design and can be compromised by astigmatic thermal lensing [1]. Here we report the investigation and successful operation of a non-astigmatic compact design of a unidirectional wavelength tunable Alexandrite ring laser with single frequency operation.
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Conference paperSoltan A, Maaskant P, Armstrong N, et al., 2019,
Wearable Glasses for Retinal Pigmentiosa Based on Optogenetics
, IEEE International Symposium on Circuits and Systems (IEEE ISCAS), Publisher: IEEE, ISSN: 0271-4302 -
Conference paperGorlitz F, Lightley J, Kumar S, et al., 2019,
Automated multiwell plate STORM: towards open source super-resolved high content analysis
, Conference on Advances in Microscopic Imaging II, Publisher: SPIE-INT SOC OPTICAL ENGINEERING, ISSN: 0277-786X- Author Web Link
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- Citations: 1
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Conference paperHarput S, Fong LH, Stanziola A, et al., 2019,
Super-Resolution Ultrasound Image Filtering with Machine-Learning to Reduce the Localization Error
, IEEE International Ultrasonics Symposium (IUS), Publisher: IEEE, Pages: 2118-2121, ISSN: 1948-5719- Author Web Link
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- Citations: 2
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Conference paperHarput S, Zhang G, Toulemonde M, et al., 2019,
Activation and 3D Imaging of Phase-change Nanodroplet Contrast Agents with a 2D Ultrasound Probe
, IEEE International Ultrasonics Symposium (IUS), Publisher: IEEE, Pages: 2275-2278, ISSN: 1948-5719- Author Web Link
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- Citations: 2
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Conference paperZhang G, Harput S, Shah A, et al., 2019,
Photoacoustic Super-Resolution Imaging using Laser Activation of Low-Boiling-Point Dye-Coated Nanodroplets in vitro and in vivo
, IEEE International Ultrasonics Symposium (IUS), Publisher: IEEE, Pages: 944-947, ISSN: 1948-5719- Author Web Link
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- Citations: 1
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Conference paperSathian J, Lian W, Minassian A, et al., 2019,
Brightness-Enhanced Solid-State Light Sources: From Kaleidoscope Effect to Uniform Illumination
, Conference on Lasers and Electro-Optics Europe / European Quantum Electronics Conference (CLEO/Europe-EQEC), Publisher: IEEE -
Conference paperSathian J, Minassian A, Alford NM, et al., 2019,
Enhancing Performance of Ce:YAG Luminescent Concentrators for High Power Applications
, Conference on Lasers and Electro-Optics Europe / European Quantum Electronics Conference (CLEO/Europe-EQEC), Publisher: IEEE -
Conference paperTawy G, Damzen MJ, 2019,
Tunable and Dual Wavelength Alexandrite Laser Using the Crystal Birefringence
, Conference on Lasers and Electro-Optics Europe / European Quantum Electronics Conference (CLEO/Europe-EQEC), Publisher: IEEE -
Conference paperTawy G, Wang J, Damzen MJ, 2019,
Population Lensing in Alexandrite Lasers
, Conference on Lasers and Electro-Optics Europe / European Quantum Electronics Conference (CLEO/Europe-EQEC), Publisher: IEEE -
Conference paperSathian J, Tawy G, Shen X, et al., 2019,
Compact Non-Astigmatic Alexandrite Ring Laser with Unidirectional Single-Longitudinal-Mode operation
, Conference on Lasers and Electro-Optics Europe / European Quantum Electronics Conference (CLEO/Europe-EQEC), Publisher: IEEE -
Conference paperZhang G, Harput S, Zhu J, et al., 2019,
Minimization of Nanodroplet Activation Time using Focused-Pulses for Droplet-Based Ultrasound Super-Resolution Imaging
, IEEE International Ultrasonics Symposium (IUS), Publisher: IEEE, Pages: 372-375, ISSN: 1948-5719- Author Web Link
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- Citations: 3
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Conference paperBrown J, Kolas S, Christensen-Jeffries K, et al., 2018,
Development of Simultaneous Optical Imaging and Super-Resolution Ultrasound to Improve Microbubble Localization Accuracy
, IEEE International Ultrasonics Symposium (IUS), Publisher: IEEE, ISSN: 1948-5719 -
Conference paperHarput S, Christensen-Jeffries K, Brown J, et al., 2018,
3-D super-resolution ultrasound (SR-US) imaging using a 2-D sparse array with high volumetric imaging rate
, IEEE International Ultrasonics Symposium (IUS), Publisher: IEEESuper-resolution ultrasound imaging has been sofar achieved in 3-D by mechanically scanning a volume witha linear probe, by co-aligning multiple linear probes, by usingmultiplexed 3-D clinical ultrasound systems, or by using 3-D ultrasound research systems. In this study, a 2-D sparsearray was designed with 512 elements according to a density-tapered 2-D spiral layout and optimized to reduce the sidelobesof the transmitted beam profile. High frame rate volumetricimaging with compounded plane waves was performed usingtwo synchronized ULA-OP256 systems. Localization-based 3-Dsuper-resolution images of two touching sub-wavelength tubeswere generated from a 120 second acquisition.
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Conference paperHarput S, Christensen-Jeffries K, Brown J, et al., 2018,
3-D motion correction for volumetric super-resolution ultrasound (SR-US) imaging
, IEEE International Ultrasonics Symposium (IUS) 2018, Publisher: IEEEMotion during image acquisition can cause imagedegradation in all medical imaging modalities. This is particularlyrelevant in 2-D ultrasound imaging, since out-of-plane motioncan only be compensated for movements smaller than elevationalbeamwidth of the transducer. Localization based super-resolutionimaging creates even a more challenging motion correction taskdue to the requirement of a high number of acquisitions to forma single super-resolved frame.In this study, an extension of two-stage motion correctionmethod is proposed for 3-D motion correction. Motion estimationwas performed on high volumetric rate ultrasound acquisitionswith a handheld probe. The capability of the proposed methodwas demonstrated with a 3-D microvascular flow simulation tocompensate for handheld probe motion. Results showed that two-stage motion correction method reduced the average localizationerror from 136 to 18μm.
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Conference paperChristensen-Jeffries K, Harput S, Brown J, et al., 2018,
3D In Vitro Ultrasound Super-Resolution Imaging using a Clinical System
, IEEE International Ultrasonics Symposium (IUS), Publisher: IEEE, ISSN: 1948-5719 -
Conference paperZhang G, Harput S, Hu H, et al., 2018,
Fast Acoustic Wave Sparsely Activated Localization Microscopy (fast-AWSALM) using Octafluoropropane Nanodroplets
, IEEE International Ultrasonics Symposium (IUS), Publisher: IEEE, ISSN: 1948-5719 -
Journal articleKerridge-Johns W, Damzen MJ, 2018,
Vortex laser from anti-resonant ring coupled cavities
, Optics Express, Vol: 26, Pages: 32839-32846, ISSN: 1094-4087Optical vortex Laguerre-Gaussian (LG0l) modes have wide-ranging applications due to their annular spatial form and orbital angular momentum. Their direct generation from a laser is attractive, due to the pure and high-power modes possible; however, previous demonstrations have had limited ranges of applicability. Here, we propose and implement direct LG0l vortex mode generation with an anti-resonant ring (ARR) coupled laser cavity geometry, where the gain medium inside the ARR is shared between two laser cavities. This generation uses standard wavelength-insensitive optical components, is suitable for high peak and average power levels, and could be applied to any bulk gain medium in pulsed or continuous wave regimes. This work demonstrates the technique with a diode end-pumped Nd:YVO4 gain medium. From 24 W of pump power, 8.9 W LG01 and 4.3 W LG02 modes were generated, all with high mode purity and pure handedness. The LG01 mode handedness was controlled with a new technique.
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Journal articleFrench P, Davis S, Wisniewski L, et al., 2018,
Slice-illuminated optical projection tomography
, Optics Letters, Vol: 43, Pages: 5555-5558, ISSN: 0146-9592To improve the imaging performance of optical projection tomography (OPT) in live samples, we have explored a parallelized implementation of semi-confocal line illumination and detection to discriminate against scattered photons. Slice-illuminated OPT (sl-OPT) improves reconstruction quality in scattering samples by reducing interpixel crosstalk at the cost of increased acquisition time. For in vivo imaging, this can be ameliorated through the use of compressed sensing on angularly undersampled OPT data sets. Here, we demonstrate sl-OPT applied to 3D imaging of bead phantoms and live adult zebrafish.
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Journal articleSheng X, Tawy G, Sathian J, et al., 2018,
Unidirectional single-frequency operation of a continuous-wave Alexandrite ring laser with wavelength tunability
, Optics Express, Vol: 26, Pages: 31129-31136, ISSN: 1094-4087High resolution spectroscopy, metrology and quantum technologies (e.g. trapping and cooling) require precision laser sources with narrow linewidth and wavelength tunability. The widespread use of these lasers will be promoted if they are cost-effective, compact and efficient. Alexandrite lasers with a broad tuning band pumped efficiently by low-cost red diodes are a potential candidate, but full performance as a precision light source has not been fully achieved. We present in this work the first continuous-wave (CW) and single-frequency operation of a unidirectional diode-end-pumped Alexandrite ring laser with wavelength tunability. An ultra-compact bow-tie ring cavity is developed with astigmatic compensation and a novel ‘displaced mode’ design producing CW output power > 1 W in excellent TEM00 mode (M2 < 1.2) when using a low brightness pump (M2 ≥ 30). Wavelength tuning from 727 - 792 nm is demonstrated using a birefringent filter plate. This successful operation opens the prospects of precision light source applications.
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Journal articleGorlitz F, Guldbrand S, Runcorn T, et al., 2018,
easySLM-STED: stimulated emission depletion microscopy with aberration correction, extended field of view and multiple beam scanning
, Journal of Biophotonics, Vol: 11, ISSN: 1864-063XWe demonstrate a simplified set‐up for STED microscopy with a straightforward alignment procedure that uses a single spatial light modulator (SLM) with collinear incident excitation and depletion beams to provide phase modulation of the beam profiles and correction of optical aberrations. We show that this approach can be used to extend the field of view for STED microscopy by correcting chromatic aberration that otherwise leads to walk‐off between the focused excitation and depletion beams. We further show how this arrangement can be adapted to increase the imaging speed through multibeam excitation and depletion. Fine adjustments to the alignment can be accomplished using the SLM only, conferring the potential for automation.
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Journal articleSoltan A, Barrett JM, Maaskant P, et al., 2018,
A head mounted device stimulator for optogenetic retinal prosthesis
, Journal of Neural Engineering, Vol: 15, ISSN: 1741-2552Objective. Our main objective is to demonstrate that compact high radiance gallium nitride displays can be used with conventional virtual reality optics to stimulate an optogenetic retina. Hence, we aim to introduce a non-invasive approach to restore vision for people with conditions such as retinitis pigmentosa where there is a remaining viable communication link between the retina and the visual cortex. Approach. We design and implement the headset using a high-density µLED matrix, Raspberry Pi, microcontroller from NXP and virtual reality lens. Then, a test platform is developed to evaluate the performance of the headset and the optical system. Furthermore, image simplification algorithms are used to simplify the scene to be sent to the retina. Moreover, in vivo evaluation of the genetically modified retina response at different light intensity is discussed to prove the reliability of the proposed system. Main results. We demonstrate that in keeping with regulatory guidance, the headset displays need to limit their luminance to 90 kcd m−2. We demonstrate an optical system with 5.75% efficiency which allows for 0.16 mW mm−2 irradiance on the retina within the regulatory guidance, but which is capable of an average peak irradiance of 1.35 mW mm−2. As this is lower than the commonly accepted threshold for channelrhodopsin-2, we demonstrate efficacy through an optical model of an eye onto a biological retina. Significance. We demonstrate a fully functional 8100-pixel headset system including software/hardware which can operate on a standard consumer battery for periods exceeding a 24 h recharge cycle. The headset is capable of delivering enough light to stimulate the genetically modified retina cells and also keeping the amount of light below the regulation threshold for safety.
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