R. R. Thomson

Heriot-Watt University, Edinburgh, SCT, United Kingdom

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Publications (83)130.58 Total impact

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    ABSTRACT: The spectral resolution of a dispersive spectrograph is limited by the width of the entrance slit. This inherently means that astronomical spectrographs trade-off throughput with spectral resolving power. Recently, optical guided-wave transitions known as 'photonic-lanterns' have been proposed to circumvent this trade-off, by enabling the efficient reformatting of multimode light into a pseudo-slit which is highly multimode in one axis, but diffraction-limited in the other. Here, we demonstrate the successful reformatting of a telescope point-spread-function into such a slit using a three-dimensional integrated optical waveguide device, which we name the 'photonic-dicer'. Using the CANARY Adaptive-Optics system on the William Herschel Telescope, and broadband celestial light between 1350 nm and 1550 nm, the device exhibits throughputs of 19.5%, 10.5% and 9.0%, under closed-loop, open-loop and tip-tilt modes of operation respectively. This work clearly demonstrates that integrated photonic technologies can facilitate new astronomical instruments with higher spectral resolution and increased efficiency.
    02/2014;
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    ABSTRACT: We report on the ultrafast laser inscription (ULI) of volume phase gratings inside gallium lanthanum sulphide (GLS) chalcogenide glass substrates. The effect of laser pulse energy and grating thickness on the dispersive properties of the gratings is investigated, with the aim of improving the performance of the gratings in the mid-infrared. The grating with the optimum performance in the mid-infrared exhibited a 1st order absolute diffraction efficiency of 61% at 1300 nm and 24% at 2640 nm. Based on the work reported here, we conclude that ULI is promising for the fabrication of mid-infrared volume phase gratings, with potential applications including astronomical instrumentation and remote sensing. This paper was published in Optical Materials Express and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: http://www.opticsinfobase.org/ome/abstract.cfm?uri=ome-3-10-1616. Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law.
    Optical Materials Express 09/2013; 3(10):1616-1624. · 2.62 Impact Factor
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    ABSTRACT: This the copy of a presentation given by David Lee at the National Astronomy Meeting in St. Andrews on 2 July 2013. Abstract: The aim of Astrophotonics is to develop high performance astronomical instrumentation which is both more compact and lower cost than existing instrumentation. Astrophotonics uses optical building blocks provided by photonics devices that were originally developed for the telecommunications industry but their design is now being modified and enhanced for use in future astronomical instruments. The reliable manufacture of this technology has recently been made possible by the technique of ultrafast laser inscription, whereby a high power laser beam is used to directly write photonics structures, such as diffraction gratings, within glass substrates. We will provide an overview of the various Astrophotonics optical devices being developed at Heriot-Watt University and STFC using the manufacturing technique of laser inscription. We will present preliminary results of laser inscribed fibre coupling systems and diffraction gratings and an overview of other systems being developed. Finally we will show how these photonics building blocks can be linked together to form a high performance miniature astronomical spectrograph. Ultimately our aim is the production of a spectrometer on a chip which will form the basis of instruments providing high multiplex observing capability.
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    David Lee, Robert R. Thomson, Colin R. Cunningham
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    ABSTRACT: This is a copy of the power point presentation given by David Lee at the Astronomical Instrumentation conference in Amsterdam (2012).
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    ABSTRACT: We report passive mode-locking of an Er-doped fiber laser using carbon nanotubes deposited on the facet of a right-angle optical waveguide.
    Lasers and Electro-Optics Pacific Rim (CLEO-PR), 2013 Conference on; 01/2013
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    ABSTRACT: We present an evanescent-field device based on a right-angled waveguide. This consists of orthogonal waveguides, with their points of intersection lying along an angled facet of the chip. Light guided along one waveguide is incident at the angled dielectric-air facet at an angle exceeding the critical angle, so that the totally internally reflected light is coupled into the second waveguide. By depositing a nanotube film on the angled surface, the chip is then used to mode-lock an Erbium doped fiber ring laser with a repetition rate of 26 MHz, and pulse duration of 800 fs.
    Applied Physics Letters 01/2013; 103(22):221117-221117-5. · 3.79 Impact Factor
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    ABSTRACT: Recent results from our work using ultrafast laser writing to fabricate waveguides and on-chip devices inside sulphide chalcogenide glasses are presented in this paper. Low loss single-mode (SM) and multi-mode (MM) waveguide arrays were successfully laser fabricated, for the first time to our knowledge, for operation in the whole near-IR (NIR) to mid- IR (MIR) range (1 to 11 μm wavelengths). These waveguides are demonstrated to have numerical apertures (NA) which can exceed NA=0.2, therefore also allowing for low bend losses as well as direct coupling to QC lasers. We also demonstrate the control over the waveguide mode field diameters (MFDs) (at 1/e2) by changing the waveguide core sizes and index contrasts, achieving typical values of 44 μm at 10.6 μm, down to 6 μm for telecom 1.55 μm light. The optical nonlinear properties of these waveguides have also been preliminarily investigated. Using a femtosecond (fs) optical parametric amplifier system, the optical nonlinearity of bulk gallium lanthanum sulphide (GLS) glass was first measured at 2.5 μm. The upper limits for the nonlinear properties of the laser modified material could be estimated based upon the nonlinear spectral broadening of a 2.5 μm fs pulse train coupled into SM waveguides. Further work includes the demonstration of on-chip three dimensional (3D) beam combiners for the MIR range (10.6 μm in this work), for near future implementation in astronomical observatories for stellar interferometry.
    Proc SPIE 09/2012;
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    ABSTRACT: It is shown that grisms, a grating and prism combination, are a simple way to achieve chromatic control in 3D multi-plane imaging. A pair of grisms, whose separation can be varied, provide a collimated beam with a tuneable chromatic shear from a collimated polychromatic input. This simple control permits the correction of chromatic smearing in 3D imaging using off-axis Fresnel zone plates and improved control of the axial profile of a focussed spot in multi-photon experiments.
    Optics Express 08/2012; 20(18):20705-14. · 3.55 Impact Factor
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    ABSTRACT: This article reports the advances on the development of mid-infrared integrated optics for stellar interferometry. The devices are fabricated by laser writing techniques on chalcogenide glasses. Laboratory characterizaton is reported and analyzed.
    Proc SPIE 07/2012;
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    David Lee, Robert R. Thomson, Colin R. Cunningham
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    ABSTRACT: Ultrafast laser inscription (ULI) is a rapidly maturing technique which uses focused ultrashort laser pulses to locally modify the refractive index of dielectric materials in three-dimensions (3D). Recently, ULI has been applied to the fabrication of astrophotonic devices such as integrated beam combiners, 3D integrated waveguide fan-outs and multimode-to-single mode convertors (photonic lanterns). Here, we outline our work on applying ULI to the fabrication of volume phase gratings (VPGs) in fused silica and gallium lanthanum sulphide (GLS) glasses. The VPGs we fabricated had a spatial frequency of 333 lines/mm. The optimum fused silica grating was found to exhibit a first order diffraction efficiency of 40 % at 633 nm, but exhibited approximately 40 % integrated scattered light. The optimum GLS grating was found to exhibit a first order diffraction efficiency of 71 % at 633 nm and less than 5 % integrated scattered light. Importantly for future astronomy applications, both gratings survived cooling to 20 K. This paper summarises the grating design and ULI manufacturing process, and provides details of the diffraction efficiency performance and blaze curves for the VPGs. In contrast to conventional fabrication technologies, ULI can be used to fabricate VPGs in almost any dielectric material, including mid-IR transmitting materials such as the GLS glass used here. Furthermore, ULI potentially provides the freedom to produce complex groove patterns or blazed gratings. For these reasons, we believe that ULI opens the way towards the development of novel VPGs for future astronomy related applications.
    Proc SPIE 07/2012;
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    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 through put loss of ≈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 ≈1.7  dB. With adequate development, similar devices could efficiently reformat the output of so-called "photonic lanterns" fabricated using highly multicore fibers.
    Optics Letters 06/2012; 37(12):2331-3. · 3.39 Impact Factor
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    ABSTRACT: We present here our recent progress in the three-dimensional (3D) direct laser writing (DLW) of step-index core waveguides inside diverse technologically relevant dielectric substrates, with specific emphasis on the demonstration of DLW mid-infrared waveguiding in the whole transparency range of these materials.
    06/2012;
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    ABSTRACT: Laser slope efficiencies close to the quantum defect limit and in excess of 78% have been obtained from an ultrafast laser inscribed buried channel waveguide fabricated in a ytterbium-doped bismuthate glass. The simultaneous achievement of low propagation losses and preservation of the fluorescence properties of ytterbium ions is the basis of the outstanding laser performance.
    Optics Letters 05/2012; 37(10):1691-3. · 3.39 Impact Factor
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    ABSTRACT: We present initial results of the direct observation of the signature of localized light in an ultrafast laser-inscribed (ULI) disordered lattice that contains an array of evanescently coupled, one-dimensional optical waveguides in glass in which certain amount of disorder in refractive index was introduced. Numerical simulations were carried out to test the feasibility of the initial experimental design. Such configurable ULI disordered waveguide lattices should open up a platform for investigating the phenomenon of transverse localization of light and its statistical nature.
    Applied Physics Letters 03/2012; 100(10):101102-101102-4. · 3.79 Impact Factor
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    ABSTRACT: We report the fabrication of high-strength (>30 dB) first order Bragg-grating waveguides in borosilicate glass substrates using ultrafast laser inscription. The cross section of each waveguide was controlled using the well known multiscan fabrication technique, where the desired waveguide cross section is constructed by scanning the sample through the laser focus multiple times. In order to fabricate high-strength gratings, it was therefore necessary to precisely control and spatially synchronize the refractive index modulations imprinted in the material by each scan. The Bragg-grating waveguides were inscribed using a femtosecond fiber laser that was externally modulated using an acousto-optic modulator. The required precision in the laser modulation was thus achieved by triggering the acousto-optic modulator using a position sensitive trigger signal supplied by the substrate translation stages themselves.
    Optics Letters 02/2012; 37(4):491-3. · 3.39 Impact Factor
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    ABSTRACT: We report the fabrication of single-mode buried channel waveguides for the whole mid-IR transparency range of chalcogenide sulphide glasses (λ ≤ 11 μm), by means of direct laser writing. We have explored the potential of this technology by fabricating a prototype three-dimensional three-beam combiner for future application in stellar interferometry that delivers a monochromatic interference visibility of 99.89% at 10.6 μm and an ultrahigh bandwidth (3-11 μm) interference visibility of 21.3%. These results demonstrate that it is possible to harness the whole transparency range offered by chalcogenide glasses on a single on-chip instrument by means of direct laser writing, a finding that may be of key significance in future technologies such as astrophotonics and biochemical sensing.
    Optics Letters 02/2012; 37(3):392-4. · 3.39 Impact Factor
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    ABSTRACT: We report the successful fabrication of mid-infrared waveguides written in a gallium lanthanum sulphide (GLS) substrate via the ultrafast laser inscription technique. Single mode guiding at 2485 nm and 3850 nm is observed. Spectral broadening spanning 1500 nm (-15dB points) is demonstrated under 3850 nm excitation.
    Optics Express 01/2012; 20(2):1545-51. · 3.55 Impact Factor
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    ABSTRACT: Ultrafast laser inscription (ULI) has been used to fabricate an 18 mm long sub-surface optical waveguide in fused silica. The waveguide started and terminated 75 $\mu{\rm m}$ below the substrate surface, approaching it to a minimum depth of $6\pm 1\ \mu{\rm m}$ for the central section. The device was fabricated in a single step, exhibiting a fiber-to-fiber insertion loss of 2.6 dB. When a high refractive index oil was placed on the substrate surface, the polarization-averaged waveguide insertion loss increased by 3.7 dB. This work demonstrates that a single ULI stage can be used to fabricate optical waveguides sufficiently close to a substrate surface for evanescent field sensing applications.
    IEEE Sensors Journal 01/2012; 12(5):1263-1266. · 1.48 Impact Factor
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    ABSTRACT: We report the fabrication of single-mode buried channel waveguides for the whole mid-IR transparency range of chalcogenide sulphide glasses (λ ≤ 11 μm), by means of direct laser writing. We have explored the potential of this technology by fabricating a prototype three-dimensional three-beam combiner for future application in stellar interferometry that delivers a monochromatic interference visibility of 99.89% at 10.6 μm and an ultrahigh bandwidth (3–11 μm) interference visibility of 21.3%. These results demonstrate that it is possible to harness the whole transparency range offered by chalcogenide glasses on a single on-chip instrument by means of direct laser writing, a finding that may be of key significance in future technologies such as astrophotonics and biochemical sensing.
    Optics Letters. 12/2011; 37(3):392-394.
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    ABSTRACT: A novel technique was used to control the spatial overlap of the orthogonal linearly polarized waveguide modes in ultrafast laser inscribed BiB(3)O(6) waveguides. We report that the strain fields induced by the expansion of material in the laser focus can be considered independently in the design of "type II" waveguides guiding orthogonal linearly polarized light. The waveguide with the optimal mode overlap was used for type I birefringently phase-matched second-harmonic generation of a continuous wave laser source at 1047 nm.
    Optics Letters 12/2011; 36(23):4548-50. · 3.39 Impact Factor

Publication Stats

273 Citations
130.58 Total Impact Points

Institutions

  • 2005–2012
    • Heriot-Watt University
      • • Department of Physics
      • • School of Engineering and Physical Sciences
      Edinburgh, SCT, United Kingdom
  • 2009–2011
    • University of St Andrews
      • School of Physics and Astronomy
      Saint Andrews, SCT, United Kingdom