Imaging biological tissue at extended depth using swept-source visible-light OCT

We present a swept-source visible-light optical coherence tomography (SS-vis-OCT) system with twice the imaging depth of prior SS-vis-OCT and improved sensitivity for imaging biological samples, achieving shot-noise-limited operation. Because second-harmonic generation is limited by the booster optical amplifier's output power, the visible-light SS power is capped at 450 µW. Increasing it further would require a more powerful, but costlier, amplifier. Instead, we reduce the receiver noise floor by selecting a balanced detector with NEP approaching the thermal (Johnson-Nyquist) limit. Real-time numerical k-linearization increases the effective number of linear-in-wavenumber samples per sweep, further improving SNR and extending the imaging range. Together, these improvements yield a sensitivity of 89 dB and an imaging depth of 9 mm in air or 6.5 mm in tissue, enabling full anterior-segment imaging of ex vivo porcine eyes.