Gallium Nitride Super-Luminescent Light Emitting Diodes for Optical Coherence Tomography Applications

Optical coherence tomography (OCT) exploits the coherent properties of light to permit noninvasive and in situ imaging of biological tissues. By expanding the range of OCT light sources from the traditional telecoms wavelengths to include ~400 nm gallium nitride (GaN) based superluminescent light emitting diodes (SLEDs) subcellular axial and lateral resolution could be achieved, provided enhanced bandwidth is also achieved. Due to the focus on high-power applications for GaN SLEDs, there has been limited work on increasing the source bandwidth. In this paper, we demonstrate for the first time a ~400 nm GaN SLED with >10 nm bandwidth employed within an OCT system, where an axial resolution of ~7 μm is achieved. Bespoke GaN SLEDs suggest that <;4 μm axial resolution imaging is imminent for short wavelength devices.