Micro-Optical Integration of Broadband Light Sources for High-Resolution Imaging

Micro-optical integration is a technique where various optical components with typical dimensions in the range of 0.3 mm to 1.5 mm are arranged on a free-space platform to deliver an integrated and compact optical module. Such integrated optical modules may collapse larger optical arrangements into a small formfactor to reduce the size of a system, or to increase the robustness of free-space optical architectures against shock and vibration, or to eliminate long-term drifts and misalignments. Micro-optical integration may also allow enhancing the performance or functionality of optical modules. For example, several semiconductor-based light sources operating at different wavelengths, such as Fabry-Perot laser diodes (LDs) or broadband Superluminescent Diodes (SLEDs), can be integrated into a compact optical module to deliver more power, multiple colors or broader optical bandwidth than conventional optical modules. In this work here, we are presenting an ultra-compact combined-SLED source with four broadband emitters at center wavelengths of 760 nm, 800 nm, 840 nm and 880 nm that are spectrally combined to an ultra-broadband output spectrum with a 3dB bandwidth of more than 165 nm around a center wavelength of 830 nm, delivering 15 mW of total power in a single-mode or polarization-maintaining output fiber. Such ultra-broadband SLED light sources enable the next generation of high-resolution biomedical imaging systems, for instance ultra-high-resolution (UHR) optical coherence tomography (OCT) systems with an axial resolution of better than two microns to achieve cellular resolution in tissue.