Swept-source visible-light optical coherence tomography

We demonstrate the feasibility of swept-source visible-light optical coherence tomography (SS-vis-OCT). We used a fanout periodically poled lithium niobate (PPLN) crystal for second harmonic generation (SHG) to convert a commercial near-infrared swept-source (NIR-SS) laser into a visible-light SS laser. To enhance SHG efficiency, we amplified the NIR-SS output with booster optical amplifiers (BOAs). We experimentally characterized SS-vis-OCT performance using two different BOAs, one yielding a visible-light output with a 48 nm bandwidth and 60 μW of power, while the other produced a 22 nm bandwidth and 680 μW of power. The SS-vis-OCT achieved a maximum axial resolution of 7.3 µm and an imaging depth of 5 mm in air, corresponding to 5.4 µm and 3.7 mm in tissue (n=1.35). Compared with spectral-domain vis-OCT using a supercontinuum laser, SS-vis-OCT provides a 3.3-fold increased imaging depth and a 2.8-fold improved roll-off. Additionally, we validated SS-vis-OCT performance using a 3D-printed pyramid phantom, with its feature measurements cross-validated by scanning electron microscopy (SEM).