Marschall Sebastian, Klein Thomas, Wieser Wolfgang, Biedermann Benjamin R, Hsu Kevin, Hansen Kim P, Sumpf Bernd, Hasler Karl-Heinz, Erbert Götz, Jensen Ole B, Pedersen Christian, Huber Robert, Andersen Peter E
DTU Fotonik, Department of Photonics Engineering, Technical University of Denmark, Frederiksborgvej 399, 4000 Roskilde, Denmark.
Opt Express. 2010 Jul 19;18(15):15820-31. doi: 10.1364/OE.18.015820.
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 microm in air (approximately 11 microm 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.
虽然1050纳米范围内的扫频光源光学相干断层扫描（OCT）在视网膜成像方面很有前景，但也存在一些挑战。传统的半导体增益介质输出功率有限，高速傅里叶域锁模（FDML）激光器的性能在标准光纤中会受到色散的影响。我们开发了一种以锥形放大器作为增益介质的新型光源，并通过比较两条具有不同色散特性的光纤延迟线来研究FDML性能。我们在谐振器中引入了一个额外的增益元件，从而实现了稳定的FDML运行，尽管色散很高，但仍能利用锥形放大器的全带宽。该光源的重复频率为116 kHz，有效平均输出功率超过30 mW。在总扫描范围为70纳米的情况下，我们在OCT测量中实现了空气中15微米的轴向分辨率（在组织中约为11微米）。正如我们的工作所示，锥形放大器是适用于1050纳米扫频光源的增益介质，可提高输出功率，而高增益可抵消FDML激光器中的色散效应。
