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.
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Graham R. Goldberg, Pavlo Ivanov, Nobuhiko Ozaki, David T. D. Childs, Kristian M. Groom, Kenneth L. Kennedy, Richard A. Hogg, "Gallium nitride light sources for optical coherence tomography," Proc. SPIE 10104, Gallium Nitride Materials and Devices XII, 101041X (16 February 2017);