William N. MacPherson
Heriot-Watt University
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Featured researches published by William N. MacPherson.
Optics Letters | 2003
Gordon M. H. Flockhart; William N. MacPherson; James S. Barton; Julian D. C. Jones; Lin Zhang; Ian Bennion
We describe what is to our knowledge the first use of fiber Bragg gratings written into three separate cores of a multicore fiber for two-axis curvature measurement. The gratings act as independent, but isothermal, fiber strain gauges for which local curvature determines the difference in strain between cores, permitting temperature-independent bend measurement.
Optics Express | 2007
Robert R. Thomson; Henry T. Bookey; Nicholas D. Psaila; Amanda Fender; Stuart Campbell; William N. MacPherson; James S. Barton; Derryck T. Reid; Ajoy K. Kar
A three dimensional fan-out device has been fabricated using ultrafast laser inscription. The device allows each core of a multicore fibre to be addressed individually by a single mode fiber held in an FVA.
Optics Letters | 2005
Amanda Fender; William N. MacPherson; James S. Barton; Julian D. C. Jones; Donghui Zhao; Helen L. Dobb; David J. Webb; Lin Zhang; Ian Bennion
We have measured the optical phase sensitivity of fiber based on poly(methyl methacrylate) under near-single-mode conditions at 632.8 nm wavelength. The elongation sensitivity is 131 +/- 3 x 10(5) rad m(-1) and the temperature sensitivity is -212 +/- 26 rad m(-1) K(-1). These values are somewhat larger than those for silica fiber and are consistent with the values expected on the basis of the bulk polymer properties.
Optics Communications | 2001
William N. MacPherson; Matthew J. Gander; Roy McBride; Julian D. C. Jones; Paul M. Blanchard; James G. Burnett; Alan H. Greenaway; Brian Joseph Mangan; T. A. Birks; Jonathan C. Knight; P. St. J. Russell
We demonstrate an all-fibre curvature sensor that uses two-core photonic crystal fibre (PCF) as the sensing element. The PCF acts as a two-beam interferometer in which phase difference is a function of curvature in the plane containing the cores. A broadband source illuminates both cores, and the spectrum at a single point in the far-field interferogram is recorded. Applying a three-wavelength phase recovery algorithm to the data provides an unambiguous measurement of the interferometer phase, and hence curvature.
Optics Express | 2005
Jonathan D. Shephard; William N. MacPherson; Robert R. J. Maier; Julian D. C. Jones; Duncan P. Hand; Mohammad Mohebbi; A. K. George; P.J. Roberts; Jonathan C. Knight
We report, for the first time, bandgap guidance above 3 mum in a silica based air-core photonic crystal fiber. The peak of the bandgap is at 3.14mum with a typical attenuation of ~ 2.6 dB m-1. By further optimization of the structure, modeling suggests that a loss below 1 dB m-1 should be achievable, greatly extending the useful operating range of silica-based single-mode fibers. Such fibers have many potential applications in the mid-IR, offering an alternative to fluoride, tellurite or chalcogenide glass based optical fibers for chemical and biological sensing applications.
IEEE Sensors Journal | 2008
Amanda Fender; William N. MacPherson; Robert R. J. Maier; James S. Barton; David S. George; Robert I. Howden; Graham W. Smith; Benjamin Jones; Scott McCulloch; Xianfeng F. Chen; Rui Suo; Lin Zhang; Ian Bennion
We report a compact two-dimensional accelerometer based upon a simple fiber cantilever constructed from a short length of multicore optical fiber. Two-axis measurement is demonstrated up to 3 kHz. Differential measurement between fiber Bragg gratings written in the multicore fiber provides temperature-insensitive measurements.
Optics Express | 2007
L. W. Kornaszewski; Nicolas Gayraud; James M. Stone; William N. MacPherson; A. K. George; Jonathan C. Knight; Duncan P. Hand; Derryck T. Reid
We demonstrate methane sensing using a photonic bandgap fiber-based gas cell and broadband idler pulses from a periodically-poled lithium niobate femtosecond optical parametric oscillator. The hollow core of the fiber was filled with a methane:nitrogen mixture, and Fourier transform spectroscopy was used to measure transmission spectra in the 3.15-3.35 mum methane absorption region. The method has applications in gas sensing for remote or hazardous environments and potentially at very low concentrations.
Optics Express | 2010
Rainer J. Beck; Jonathan P. Parry; William N. MacPherson; Andrew J. Waddie; Nicholas John Weston; Jonathan D. Shephard; Duncan P. Hand
The application of a commercially available spatial light modulator (SLM) to control the spatial intensity distribution of a nanosecond pulsed laser for micromachining is described for the first time. Heat sinking is introduced to increase the average power handling capabilities of the SLM beyond recommended limits by the manufacturer. Complex intensity patterns are generated, using the Inverse Fourier Transform Algorithm, and example laser machining is demonstrated. The SLM enables both complex beam shaping and also beam steering.
IEEE Sensors Journal | 2003
Matthew J. Gander; William N. MacPherson; James S. Barton; Robert Lewis Reuben; Julian D. C. Jones; R. Stevens; Kam S. Chana; S. J. Anderson; T. V. Jones
Small size, high bandwidth pressure sensors are required for instrumentation of probes and test models in aerodynamic studies of complex unsteady flows. Optical-fiber pressure sensors promise potential advantages of small size and low cost in comparison with their electrical counterparts. We describe miniature Fabry-Perot cavity pressure sensors constructed by micromachining techniques in a turbine test application. The sensor bodies are 500 /spl mu/m squared, 300 /spl mu/m deep with a /spl sim/2 /spl mu/m-thick copper diaphragm electroplated on one face. The sensor cavity is formed between the diaphragm and the cleaved end of a single mode fiber sealed to the sensor by epoxy. Each sensor is addressed interferometrically in reflection by three wavelengths simultaneously, giving an unambiguous phase determination; a pressure sensitivity of 1.6 radbar/sup -1/ was measured, with a typical range of vacuum to 600 kPa. Five sensors were embedded in the trailing edge of a nozzle guide vane installed upstream of a rotor in a full-scale turbine stage transient test facility. Pressure signals in the trailing edge flow show marked structure at the 8 kHz blade passing frequency. To our knowledge, this is the first report of sensors located at the trailing edge of a normal-sized turbine blade.
Applied Optics | 2008
Nicolas Gayraud; Kornaszewski Uw; James M. Stone; Jonathan C. Knight; Derryck T. Reid; Duncan P. Hand; William N. MacPherson
We demonstrate methane sensing based on Fourier transform infrared spectroscopy using a hollow-core photonic bandgap fiber guiding in the mid-infrared and idler pulses from a femtosecond optical parametric oscillator. Transmission measurements are presented for several fibers, and sensing is demonstrated using a fiber whose bandgap overlaps the methane fundamental absorption lines. The gas filling process of the air core is described, and qualitative methane concentrations measurements to 1000 ppm (parts in 10(6)) are reported. Operation down to 50 ppm based on our current experiment is predicted.