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An investigation of phase-mask diffraction patterns and fibre Bragg gratings with scanning near-field optical microscopy

An investigation of phase-mask diffraction patterns and fibre Bragg gratings with scanning near-field optical microscopy
An investigation of phase-mask diffraction patterns and fibre Bragg gratings with scanning near-field optical microscopy
In recent years, near-field microscopy has been utilized for assessing the properties of optical wave-guides at an increasing rate. Here, a Scanning Near-field Optical Microscope (SNOM) has been designed and constructed in order to expand this work into an analysis of the optical and structural properties of fibre Bragg gratings, which are used throughout the optical fibre telecommunications network. By imaging the evanescent fields of Bragg gratings, a characterization technique has been developed which has enabled the acquisition of sub-wavelength information about the optical field distribution within a fibre grating and its refractive index structure. Six separate fibre grating samples have been examined, demonstrating the feasibility of the developed scanning technique to become a useful characterization tool. In particular, the study has enabled grating standing wave fringes to be imaged relative to corresponding refractive index fringes, for the first time.

The SNOM has also been utilized to map free-space diffraction patterns close to a phase-mask (transmission diffraction grating). The patterns are normally used to create fibre gratings via UV photosensitivity mechanisms. The field distributions have been imaged under various experimental conditions and have revealed some of the technical problems that might occur during the writing of gratings. The measured patterns have also served to confirm existing diffraction grating theory, which has been expanded during the course of this work to produce a new expression for the 'Talbot length', originally formulated by Rayleigh in 1881.
Mills, J.D.
3b139ebc-5875-4367-80e6-f7e94cf2d6a8
Mills, J.D.
3b139ebc-5875-4367-80e6-f7e94cf2d6a8

Mills, J.D. (2001) An investigation of phase-mask diffraction patterns and fibre Bragg gratings with scanning near-field optical microscopy. University of Southampton, Department of Physics and Astronomy, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

In recent years, near-field microscopy has been utilized for assessing the properties of optical wave-guides at an increasing rate. Here, a Scanning Near-field Optical Microscope (SNOM) has been designed and constructed in order to expand this work into an analysis of the optical and structural properties of fibre Bragg gratings, which are used throughout the optical fibre telecommunications network. By imaging the evanescent fields of Bragg gratings, a characterization technique has been developed which has enabled the acquisition of sub-wavelength information about the optical field distribution within a fibre grating and its refractive index structure. Six separate fibre grating samples have been examined, demonstrating the feasibility of the developed scanning technique to become a useful characterization tool. In particular, the study has enabled grating standing wave fringes to be imaged relative to corresponding refractive index fringes, for the first time.

The SNOM has also been utilized to map free-space diffraction patterns close to a phase-mask (transmission diffraction grating). The patterns are normally used to create fibre gratings via UV photosensitivity mechanisms. The field distributions have been imaged under various experimental conditions and have revealed some of the technical problems that might occur during the writing of gratings. The measured patterns have also served to confirm existing diffraction grating theory, which has been expanded during the course of this work to produce a new expression for the 'Talbot length', originally formulated by Rayleigh in 1881.

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Published date: 2001
Organisations: University of Southampton

Identifiers

Local EPrints ID: 15492
URI: http://eprints.soton.ac.uk/id/eprint/15492
PURE UUID: 90eb51ba-ad5e-4072-9bf5-062ed95aa389

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Date deposited: 31 May 2005
Last modified: 11 Dec 2021 14:02

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