Coherence length extension of Fourier domain mode locked lasers

Fourier domain mode locked (FDML) lasers provide high sweep rates, broad tuning ranges, and high output powers for optical coherence tomography (OCT) systems. However, presently-known FDML lasers at 1300 nm have relatively short coherence lengths, limiting the size of samples that can be imaged. Furthermore, FDML lasers produce only one useable sweep direction. We report FDML coherence length extension by incorporating advanced dispersion compensation modules (DCMs). DCMs eliminate group velocity dispersion in the cavity, doubling coherence lengths and ensuring uniform axial resolution over the imaging range. Additionally, forward and backward sweeps are nearly identical, removing the need for external buffering stages.