Narrow–linewidth tunable laser source for long-wavelength optical coherence tomography at 1700 nm

\nWe present a widely tunable laser source with narrowed linewidths at the level of 0.4 – 1.1 nm. The laser source incorporates a comb-profile fiber (CPF) which allows for spectral compression of the tunable optical pulses to the linewidths below 1 nm. The spectral compression factor is as high as 37.2 and is the highest obtained for this wavelength range. With the use of an electro-optic modulator (EOM), the laser system ensures rapid tuning up to 10 GHz. Together with the wide spectral range of 1600-1900 nm, and compressed spectral width, the source meets the requirements of the optical coherence tomography (OCT).\n