Phase-sensitive optical coherence tomography using buffered Fourier domain mode-locked lasers at up to 370,000 scans per second

Phase sensitive optical coherence tomography (OCT) can be used to obtain sub-nanometer displacement measurements of biological and non-biological samples. This technique has many applications, including detection of small amplitude surface motion, and high axial resolution OCT phase microscopy. Doppler OCT is another type of phase sensitive imaging, where differential phase measurements are used to detect fluid flow in biological specimens. For all types of phase sensitive OCT, a light source with low phase noise is required in order to provide good displacement sensitivity. High speed imaging is also necessary in order to minimize motion artifacts and enable the detection of fast transient events. In this manuscript, buffered Fourier Domain Mode Locked (FDML) lasers are demonstrated for ultrahigh-speed phase sensitive OCT detection. The lasers are operated at sweep speeds of 42, 117, and 370 kHz, and displacement sensitivities of 39, 52, and 102 pm are achieved, respectively. These displacement sensitivities are comparable to spectrometer-based phase sensitive OCT systems, but acquisition speeds 1.4 - 13x faster are possible using buffered FDML lasers. An additional factor of √2 improvement in noise performance is observed for differential phase measurements, which has important implications for Doppler OCT. Dynamic measurements of rapid, small-amplitude piezoelectric transducer motion are demonstrated. In general, buffered FDML lasers provide excellent displacement sensitivities at extremely high sweep speeds for phase sensitive OCT measurements.