Stretched-pulse mode-locked wavelength-swept laser with intra- and extra-cavity stretching for ultrahigh-speed optical coherence tomography

Optical coherence tomography (OCT) is a high-resolution imaging technique that provides wide field and high-speed imaging of three-dimensional volume. Stretched-pulse mode-locked (SPML) wavelength-swept laser has recently emerged as a promising ultrahigh-speed wavelength-swept laser that provides an A-line rate up to tens of MHz. The SPML laser utilizes chromatic dispersion to generate the wavelength-swept output with repetition rates from a few mega-hertz to over 10 MHz without using any mechanical wavelength scanning filter. For a simple and compact SPML laser design, utilization of a few meter-long chirped fiber Bragg grating (CFBG) as the intra-cavity dispersion element is recently demonstrated. In this work, we present SPML wavelength-swept laser using intra- and extra-cavity CFBG for the ultrahigh-speed OCT. We investigated the performance of the SPML laser as a light source for the ultrahigh-speed OCT by utilizing a combination of intra and extra-cavity stretching. We present that the noise performance and the coherence length performance of the laser can be adjusted and optimized through a proper combination of the intra and the extra cavity stretching in the SPML laser.