Tailored Supercontinuum Generation for Shot-Noise-Limited, Ultrahigh-Resolution Optical Coherence Tomography at 1.3 µm

Achieving shot-noise-limited sensitivity in spectral-domain optical coherence tomography (SD-OCT) while attaining ultrahigh axial resolution with broadband sources remains challenging, as spectral broadening typically introduces excess noise. To overcome this limitation, we propose a tailored supercontinuum generation for a 1.3 µm ultra-flat, low-noise supercontinuum based on engineered nonlinear dynamics in an anomalous-dispersion highly nonlinear fiber pumped by a home-built 1.55-µm femtosecond laser. By harnessing self-phase modulation-driven soliton dynamics and phase-matched dispersive-wave generation, a smooth and reproducible spectral connection between the soliton band and the dispersive wave is achieved, yielding an exceptionally flat and broadband spectrum with near-unity coherence. The SC source provides a 3-dB bandwidth of 295.09 nm and a 10-dB bandwidth of 373.86 nm centered at 1300 nm. Variance-power analysis confirms excess noise below the shot-noise level in the dominant spectral region. Implemented in an SD-OCT system, the source achieves an axial resolution of 1.99 µm and a sensitivity of 102.02 dB. Imaging of multilayer tape and porcine myocardial tissue demonstrates enhanced contrast, resolution, and signal-to-noise ratio. This work reports the first realization of shot-noise-limited OCT with ultrahigh axial resolution, breaking the trade-off between bandwidth, spectral flatness, and noise.