Broad Wavelength Band GaSb SLEDs for Mid-IR Optical Coherence Tomography and Spectroscopy

Light sources with broad spectral emission at around 2 μm and beyond are attractive for many applications in spectroscopy and sensing. For example, such sources are needed to detect and monitor environmental gasses, industrial processes and biomarkers such as lactate, urea and glucose [1]. Notably long wavelengths penetrate deeper in certain type of materials and tissues. Specifically in media with low water content, such as teeth, mid-IR allows deeper penetration thus allowing advanced optical coherence tomography (OCT) imaging [2]. For these applications broad wavelength emission to allow multi-wavelength spectroscopy with capacity to detect multiple species with enhanced specificity, or to increase the axial resolution in OCT systems. Superluminescent diodes (SLED) are ideally positioned to serve such applications, owing to attractive features including low coherence, bright and broadband emission and ability to be used as a building block in swept-source or external cavity laser.