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190 results on '"Thomson, R R"'

1. High resolution TCSPC imaging of diffuse light with a one-dimensional SPAD array scanning system

Author

McShane, E. P., Chandrasekharan, H. K., Kufcsák, A., Finlayson, N., Erdogan, A. T., Henderson, R. K., Dhaliwal, K., Thomson, R. R., and Tanner, M. G.

Subjects
Physics - Instrumentation and Detectors, Physics - Optics
Abstract

We report a time-resolved single photon counting (TCSPC) imaging system based on a line-scanning architecture. The system benefits from the high fill-factor, active area, and large dimension of an advanced CMOS single photon avalanche diode (SPAD) array line-sensor. A two-dimensional image is constructed using a moving mirror to scan the line-sensor field-of-view (FOV) across the target, to enable the efficient acquisition of a two-dimensional 0.26 Mpixel TCSPC image. We demonstrate the capabilities of the system for TCSPC imaging and locating objects obscured in scattering media - specifically to locate a series of discrete point sources of light along an optical fibre submerged in a highly scattering solution. We demonstrate that by selectively imaging using early arriving photons which have undergone less scattering than later arriving photons, our TCSPC imaging system is able to locate the position of discrete point sources of light than a non-time-resolved imaging system., Comment: 12 pages, 5 figures submitted to Optica: Optics Express

Published
2022
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2. Simulation and Optimization of an Astrophotonic Reformatter

Author

Anagnos, Th., Harris, R. J., Corrigan, M. K., Reeves, A. P., Townson, M. J., MacLachlan, D. G., Thomson, R. R., Morris, T. J., Schwab, C., and Quirrenbach, A.

Subjects
Astrophysics - Instrumentation and Methods for Astrophysics
Abstract

Image slicing is a powerful technique in astronomy. It allows the instrument designer to reduce the slit width of the spectrograph, increasing spectral resolving power whilst retaining throughput. Conventionally this is done using bulk optics, such as mirrors and prisms, however more recently astrophotonic components known as photonic lanterns (PLs) and photonic reformatters have also been used. These devices reformat the multi-mode (MM) input light from a telescope into single-mode (SM) outputs, which can then be re-arranged to suit the spectrograph. The photonic dicer (PD) is one such device, designed to reduce the dependence of spectrograph size on telescope aperture and eliminate modal noise. We simulate the PD, by optimising the throughput and geometrical design using Soapy and BeamProp. The simulated device shows a transmission between 8 and 20 %, depending upon the type of adaptive optics (AO) correction applied, matching the experimental results well. We also investigate our idealised model of the PD and show that the barycentre of the slit varies only slightly with time, meaning that the modal noise contribution is very low when compared to conventional fibre systems. We further optimise our model device for both higher throughput and reduced modal noise. This device improves throughput by 6.4 % and reduces the movement of the slit output by 50%, further improving stability. This shows the importance of properly simulating such devices, including atmospheric effects. Our work complements recent work in the field and is essential for optimising future photonic reformatters.

Published
2018
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3. Ballistic and snake photon imaging for locating optical endomicroscopy fibres

Author

Tanner, M. G., Choudhary, T. R., Craven, T. H., Mills, B., Bradley, M., Henderson, R. K., Dhaliwal, K., and Thomson, R. R.

Subjects
Physics - Medical Physics, Physics - Biological Physics, Physics - Optics
Abstract

We demonstrate determination of the location of the distal-end of a fibre-optic device deep in tissue through the imaging of ballistic and snake photons using a time resolved single-photon detector array. The fibre was imaged with centimetre resolution, within clinically relevant settings and models. This technique can overcome the limitations imposed by tissue scattering in optically determining the in vivo location of fibre-optic medical instruments.

Published
2017
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4. Development of integrated mode reformatting components for diffraction-limited spectroscopy

Author

MacLachlan, D. G., Harris, R. J., Choudhury, D., Simmonds, R. D., Salter, P. S., Booth, M. J., Allington-Smith, J. R., and Thomson, R. R.

Subjects
Physics - Optics
Abstract

We present the results of our work on developing fully integrated devices (photonic dicers) for reformatting multimode light to a diffraction limited pseudo-slit. These devices can be used to couple a seeing-limited telescope point-spread-function to a spectrograph operating at the diffraction limit, thus enabling compact, high-resolution spectrographs that are free of modal-noise.

Published
2015
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5. The Photonic Lantern

Author

Birks, T. A., Gris-Sánchez, I., Yerolatsitis, S., Leon-Saval, S. G., and Thomson, R. R.

Subjects
Physics - Optics
Abstract

Photonic lanterns are made by adiabatically merging several single-mode cores into one multimode core. They provide low-loss interfaces between single-mode and multimode systems where the precise optical mapping between cores and individual modes is unimportant., Comment: 45 pages; article unchanged, accepted for publication in Advances in Optics and Photonics

Published
2015
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6. Ultrafast Laser Inscription of a 121-Waveguide Fan-Out for Astrophotonics

Author

Thomson, R. R., Harris, R. J., Birks, T. A., Brown, G., Allington-Smith, J., and Bland-Hawthorn, J.

Subjects
Physics - Optics, Astrophysics - Instrumentation and Methods for Astrophysics, Physics - Instrumentation and Detectors
Abstract

Using ultrafast laser inscription, we report the fabrication of a prototype three-dimensional 121-waveguide fan-out device capable of reformatting the output of a 120 core multicore fiber (MCF) into a one-dimensional linear array. When used in conjunction with an actual MCF, we demonstrate that the reformatting function using this prototype would result in an overall throughput loss of approximately 7.0 dB. However, if perfect coupling from the MCF into the fan-out could be achieved, the reformatting function would result in an overall loss of only approximately 1.7 dB. With adequate development, similar devices could efficiently reformat the output of so-called "photonic lanterns" fabricated using highly multicore fibers.

Published
2012
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8. Development of a Fiber Connectorized Ultrafast Laser Inscribed 2-Telescope Beam Combiner for the CHARA Telescope Array

Author

Benoît, A., primary, Siliprandi, J., additional, MacLachlan, D. G., additional, Ross, C. A., additional, Sharma, T. K., additional, Labadie, L., additional, Madhav, K., additional, Nayak, A. S., additional, Dinkelaker, A. N., additional, Roth, M. M., additional, Pedretti, E., additional, Ten Brummelaar, T. A., additional, Scott, N. J., additional, Du Foresto, V. Condé, additional, and Thomson, R. R., additional

Published
2023
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11. A miniature fiber optic ablation probe manufactured via ultrafast laser inscription and selective chemical etching.

Author

Ehrlich, K., Ross, C. A., Beck, R. J., Shephard, J. D., and Thomson, R. R.

Subjects
FOCUS (Optics), OPTICAL fibers, INSCRIPTIONS, FIBER optics, ETCHING, OPTICAL fiber detectors, NEEDLES & pins, HIGH-intensity focused ultrasound, FIBER lasers
Abstract

Picosecond laser ablation has recently emerged as a minimally invasive alternative to conventional surgical resection of early tumors, offering high precision and limited thermal damage to surrounding tissue. Potential clinical application routes include deployment through the working channels of endoscopes or needle bores, which require the delivery of ultrashort high energy pulses through flexible optical fibers with focusing optics at the distal end. The manufacture of distal end optical systems for fiber ablation is challenging, inhibiting translation toward clinical applications. Here, we present a miniature fiber-coupled ablation probe developed using ultrafast laser inscription and chemical etching, employing a hollow-core fiber for pulse delivery. Its design, fabrication, and characterization are detailed, along with a feasibility demonstration for the ablation of stainless steel and chicken tissue. [ABSTRACT FROM AUTHOR]

Published
2023
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17. Modal noise mitigation for high-precision spectroscopy using a photonic reformatter

Author

Universitat Politècnica de València. Instituto Universitario de Telecomunicación y Aplicaciones Multimedia - Institut Universitari de Telecomunicacions i Aplicacions Multimèdia, European Commission, Science and Technology Facilities Council, Reino Unido, Engineering and Physical Sciences Research Council, Reino Unido, Pike, F. A., Benoît, A., MacLachlan, D. G., Harris, R. J., Gris-Sánchez, Itandehui, Lee, D., Birks, T. A., Thomson, R. R., Universitat Politècnica de València. Instituto Universitario de Telecomunicación y Aplicaciones Multimedia - Institut Universitari de Telecomunicacions i Aplicacions Multimèdia, European Commission, Science and Technology Facilities Council, Reino Unido, Engineering and Physical Sciences Research Council, Reino Unido, Pike, F. A., Benoît, A., MacLachlan, D. G., Harris, R. J., Gris-Sánchez, Itandehui, Lee, D., Birks, T. A., and Thomson, R. R.

Abstract

[EN] Recently, we demonstrated how an astrophotonic light reformatting device, based on a multicore fibre photonic lantern and a 3D waveguide component, can be used to efficiently reformat the point spread function of a telescope to a diffraction-limited pseudo-slit. Here, we demonstrate how such a device can also efficiently mitigate modal noise - a potential source of instability in high-resolution multimode fibre-fed spectrographs. To investigate the modal noise performance of the photonic reformatter, we have used it to feed light into a bench-top near-infrared spectrograph (R approximate to 7000, lambda approximate to 1550 nm). One approach to quantifying the modal noise involved the use of broad-band excitation light and a statistical analysis of how the overall measured spectrum was affected by variations in the input coupling conditions. This approach indicated that the photonic reformatter could reduce modal noise by a factor of 6 when compared to a multimode fibre with a similar number of guided modes. Another approach to quantifying themodal noise involved the use of multiple spectrally narrow lines, and an analysis of how the measured barycentres of these lines were affected by variations in the input coupling. Using this approach, the photonic reformatter was observed to suppress modal noise to the level necessary to obtain spectra with stability close to that observed when using a single mode fibre feed. These results demonstrate the potential of using photonic reformatters to enable efficient multimode spectrographs that operate at the diffraction-limit and are free of modal noise, with potential applications including radial velocity measurements of M-dwarfs.

Published
2020

19. Towards Photonic Lantern-Based Microendoscopy

Author

McNicholl, D., primary, Li, S., additional, Choudhury, D., additional, Repetti, A., additional, Gris-Sauchez, I., additional, Whyte, G., additional, Birks, T. A., additional, Phillips, D. B., additional, Wiaux, Y., additional, and Thomson, R. R., additional

Published
2020
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20. Fibre Platform for Multiplexed Physiological Sensing in the Distal Lung with Fluorescent Probes on Multicore Fibres

Author

Tanner, M. G., primary, Choudhary, T. R., additional, Ehrlich, K., additional, Megia-Fernandez, A., additional, Harrington, K., additional, Wood, H. A., additional, Marshall, A., additional, Zhu, P., additional, Chankeshwara, S. V., additional, Choudhury, D., additional, Monro, G., additional, Ucuncu, M., additional, Yu, F., additional, Duncan, R. R., additional, Thomson, R. R., additional, Dhaliwal, K., additional, and Bradley, M., additional

Published
2020
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33. Endoscopic sensing of alveolar pH

Author

Choudhury, D., primary, Tanner, M. G., additional, McAughtrie, S., additional, Yu, F., additional, Mills, B., additional, Choudhary, T. R., additional, Seth, S., additional, Craven, T. H., additional, Stone, J. M., additional, Mati, I. K., additional, Campbell, C. J., additional, Bradley, M., additional, Williams, C. K. I., additional, Dhaliwal, K., additional, Birks, T. A., additional, and Thomson, R. R., additional

Published
2016
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40. The photonic lantern

Author

Birks, T. A., primary, Gris-Sánchez, I., additional, Yerolatsitis, S., additional, Leon-Saval, S. G., additional, and Thomson, R. R., additional

Published
2015
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41. Ultrafast laser inscribed Yb:KGd(WO4)2 and Yb:KY(WO4)2 channel waveguide lasers

Author

Bain, F. M., Lagatsky, A. A., Thomson, R. R., Psaila, N. D., Kuleshov, N. V., Kar, A. K., Sibbett, W., and Brown, C. T. A.

Abstract

We demonstrate laser action in diode-pumped microchip monolithic cavity channel waveguides of Yb:KGd(WO4)2 and Yb:KY(WO4)2 that were fabricated by ultrafast laser writing. The maximum output power achieved was 18.6 mW with a threshold of approximately 100 mW from an Yb:KGd(WO4)2waveguide laser operating at 1023 nm. The propagation losses for this waveguide structure were measured to be 1.9 dBcm−1.

Published
2009

43. Efficient photonic reformatting of celestial light for diffraction-limited spectroscopy.

Author

MacLachlan, D. G., Harris, R. J., Gris-Sánchez, I., Morris, T. J., Choudhury, D., Gendron, E., Basden, A. G., Spaleniak, I., Arriola, A., Birks, T. A., Allington-Smith, J. R., and Thomson, R. R.

Subjects
PHOTONICS, SPECTROGRAPHS, THEORY of wave motion, DIFFRACTION gratings, ADAPTIVE optics
Abstract

The spectral resolution of a dispersive astronomical spectrograph is limited by the trade-off between throughput and the width of the entrance slit. Photonic guided wave transitions have been proposed as a route to bypass this trade-off, by enabling the efficient reformatting of incoherent seeing-limited light collected by the telescope into a linear array of single modes: a pseudo-slit which is highly multimode in one axis but diffraction-limited in the dispersion axis of the spectrograph. It is anticipated that the size of a single-object spectrograph fed with light in this manner would be essentially independent of the telescope aperture size. A further anticipated benefit is that such spectrographs would be free of 'modal noise', a phenomenon that occurs in high-resolution multimode fibre-fed spectrographs due to the coherent nature of the telescope point spread function (PSF). We seek to address these aspects by integrating a multicore fibre photonic lantern with an ultrafast laser inscribed three-dimensional waveguide interconnect to spatially reformat the modes within the PSF into a diffraction-limited pseudo-slit. Using the CANARY adaptive optics (AO) demonstrator on the William Herschel Telescope, and 1530 ± 80 nm stellar light, the device exhibits a transmission of 47-53 per cent depending upon the mode of AO correction applied. We also show the advantage of using AO to couple light into such a device by sampling only the core of the CANARY PSF. This result underscores the possibility that a fully optimized guided-wave device can be used with AO to provide efficient spectroscopy at high spectral resolution. [ABSTRACT FROM AUTHOR]

Published
2017
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50. Frequency-doubling in femtosecond laser inscribed periodically-poled potassium titanyl phosphate waveguides

Author

Campbell, S., Thomson, R. R., Hand, D. P., Kar, A. K., Reid, D. T., Canalias, Carlota, Pasiskevicius, Valdas, Laurell, Fredrik, Campbell, S., Thomson, R. R., Hand, D. P., Kar, A. K., Reid, D. T., Canalias, Carlota, Pasiskevicius, Valdas, and Laurell, Fredrik

Abstract

Frequency doubling has been achieved in femtosecond-laser-inscribed single-mode waveguides written in two periodically-poled potassium titanyl phosphate crystals. A conversion efficiency of 0.22 %W-1 was obtained for first-order quasi-phase matching at 980 nm and an efficiency of 0.02 %W-1 for third-order quasi-phase matching at 800 nm., QC 20100525 QC 20120201

Published
2007
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