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

ABSTRACT 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.