School of Physics - Research Publications

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Author: Roberts, Ann × End date: 2018 × Subject: Optics and Opto-electronic Physics ; Physical Sciences ×

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    Precision measurement of the electromagnetic fields in the focal region of a high-numerical-aperture lens using a tapered fiber probe
    Rhodes, SK ; Nugent, KA ; Roberts, A (OPTICAL SOC AMER, 2002-08)
    We present a measurement of the intensity around the focus of a N.A.-0.95 lens using a tapered optical fiber probe. An asymmetry introduced by the vector nature of the incident polarized light is evident, although it is inconsistent with that predicted theoretically by considering the magnitude squared of the electric field. The sensitivity of the probe to different components of the electromagnetic field is considered, and it is shown that the measurement is consistent with vector diffraction theory when the probe properties are taken into account.
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    Fabrication of long-period fiber gratings by use of focused ion-beam irradiation
    von Bibra, ML ; Roberts, A ; Canning, J (OPTICAL SOC AMER, 2001-06-01)
    Long-period gratings have been made in nonphotosensitive optical fibers by irradiation of the core of a fiber with a focused beam of high-energy protons. The irradiated fibers exhibit relatively low loss, even before thermal annealing, and possess strongly wavelength-dependent transmission. The absence of a mask provides the opportunity to tailor the grating to a desired profile, and a variety of grating profiles were explored. The profile most resembling a sinusoid was found to produce the cleanest transmission spectra.
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    Refractive index profiling of axially symmetric optical fibers: a new technique
    Ampem-Lassen, E ; Huntington, ST ; Dragomir, NM ; Nugent, KA ; Roberts, A (OPTICAL SOC AMER, 2005-05-02)
    We present a new technique for determining the refractive index profiles of axially symmetric optical fibers based on imaging phase gradients introduced into a transmitted optical field by a fiber sample. An image of the phase gradients within the field is obtained using a new non-interferometric technique based on bright field microscopy. This provides sufficient information to reconstruct the refractive index profile using the inverse Abel transform. The technique is robust, rapid and possesses high spatial resolution and we demonstrate its application to the reconstruction of the refractive index profiles of a single-mode and a multimode optical fiber.
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    Nondestructive imaging of a type I optical fiber Bragg grating
    Dragomir, NM ; Rollinson, C ; Wade, SA ; Stevenson, AJ ; Collins, SF ; Baxter, GW ; Farrell, PM ; Roberts, A (OPTICAL SOC AMER, 2003-05-15)
    Nondestructive images of refractive-index variation within a type I fiber Bragg grating have been recorded by the differential interference contrast imaging technique. The images reveal detailed structure within the fiber core that is consistent with the formation of Talbot planes in the diffraction pattern behind the phase mask that had been used to fabricate the grating.