"Fourier domain mode-locked swept source
at 1050 nm based on a tapered amplifier"Sebastian Marschall, Thomas Klein, Wolfgang Wieser, Benjamin R. Biedermann, Kevin Hsu, Kim P. Hansen, Bernd Sumpf, Karl-Heinz Hasler, Götz Erbert, Ole B. Jensen, Christian Pedersen, Robert Huber, Peter E. Andersen
Optics Express Vol. 18, Issue 15, pp.15820-15831 (2010)
While swept source optical coherence tomography (OCT) in the 1050 nm range is promising for retinal imaging, there are certain challenges. Conventional semiconductor gain media have limited output power, and the performance of high-speed Fourier domain mode-locked (FDML) lasers suffers from chromatic dispersion in standard optical fiber. We developed a novel light source with a tapered amplifier as gain medium, and investigated the FDML performance comparing two fiber delay lines with different dispersion properties. We introduced an additional gain element into the resonator, and thereby achieved stable FDML operation, exploiting the full bandwidth of the tapered amplifier despite high dispersion. The light source operates at a repetition rate of 116 kHz with an effective average output power in excess of 30 mW. With a total sweep range of 70 nm, we achieved an axial resolution of 15 µm in air (~11 µm in tissue) in OCT measurements. As our work shows, tapered amplifiers are suitable gain media for swept sources at 1050 nm with increased output power, while high gain counteracts dispersion effects in an FDML laser.
BMO authors (in alphabetic order):
Fourier Domain Mode Locking (FDML): Spectral mode locking in optics and applications
Optical Coherent Ranging and Optical Coherence Tomography (OCT): Imaging and profilometry with rapidly frequency swept laser sources