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Proceedings Paper

Gallium nitride light sources for optical coherence tomography
Author(s): Graham R. Goldberg; Pavlo Ivanov; Nobuhiko Ozaki; David T. D. Childs; Kristian M. Groom; Kenneth L. Kennedy; Richard A. Hogg
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Paper Abstract

The advent of optical coherence tomography (OCT) has permitted high-resolution, non-invasive, in vivo imaging of the eye, skin and other biological tissue. The axial resolution is limited by source bandwidth and central wavelength. With the growing demand for short wavelength imaging, super-continuum sources and non-linear fibre-based light sources have been demonstrated in tissue imaging applications exploiting the near-UV and visible spectrum. Whilst the potential has been identified of using gallium nitride devices due to relative maturity of laser technology, there have been limited reports on using such low cost, robust devices in imaging systems.

A GaN super-luminescent light emitting diode (SLED) was first reported in 2009, using tilted facets to suppress lasing, with the focus since on high power, low speckle and relatively low bandwidth applications. In this paper we discuss a method of producing a GaN based broadband source, including a passive absorber to suppress lasing. The merits of this passive absorber are then discussed with regards to broad-bandwidth applications, rather than power applications. For the first time in GaN devices, the performance of the light sources developed are assessed though the point spread function (PSF) (which describes an imaging systems response to a point source), calculated from the emission spectra. We show a sub-7μm resolution is possible without the use of special epitaxial techniques, ultimately outlining the suitability of these short wavelength, broadband, GaN devices for use in OCT applications.

Paper Details

Date Published: 16 February 2017
PDF: 7 pages
Proc. SPIE 10104, Gallium Nitride Materials and Devices XII, 101041X (16 February 2017); doi: 10.1117/12.2252665
Show Author Affiliations
Graham R. Goldberg, Univ. of Glasgow (United Kingdom)
Pavlo Ivanov, Univ. of Glasgow (United Kingdom)
Nobuhiko Ozaki, Wakayama Univ. (Japan)
David T. D. Childs, Univ. of Glasgow (United Kingdom)
Kristian M. Groom, The Univ. of Sheffield (United Kingdom)
Kenneth L. Kennedy, The Univ. of Sheffield (United Kingdom)
Richard A. Hogg, Univ. of Glasgow (United Kingdom)

Published in SPIE Proceedings Vol. 10104:
Gallium Nitride Materials and Devices XII
Jen-Inn Chyi; Hiroshi Fujioka; Hadis Morkoç; Yasushi Nanishi; Ulrich T. Schwarz; Jong-In Shim, Editor(s)

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