100 MHz A-line rate optical coherence tomography using a stretched-pulse mode-locked wavelength-swept laser light source.

We report the first, to the best of our knowledge, 100 MHz stretched-pulse mode-locked (SPML) wavelength-swept laser light source and optical coherence tomography (OCT) system. The all-polarization-maintaining fiber SPML laser employs a chirped fiber Bragg grating (CFBG) with a linear-in-wavenumber intra-cavity group delay of 93 ps/nm over the 1240 - 1340 nm wavelength range, enabling a 100 nm wavelength sweep within 9.3 ns. The resulting OCT system operates at a 100 MHz A-line rate with a measured axial resolution of 13.5 µm, 90 dB sensitivity, and a 6 dB coherence length of 500 µm. To fully exploit this ultrahigh A-line rate for practical applications, a polygon-mirror-based fast-axis beam scanner is combined with a calibration-based framework that compensates polygon-scanner-induced image artifacts. System performance is demonstrated through large-field, high-speed imaging of a resolution target and high-throughput three-dimensional (3D) inspection of industrial samples, including subsurface imaging of a microSD card and quantitative conformal coating thickness mapping on printed circuit boards.