Frequency comb swept laser with a high-Q microring filter

Frequency comb swept lasers are the enabling technology of circular interferometric imaging.which was proposed to break the bottleneck of data acquisition and proessing in optical coherence tomography(OCT)at video rate.In this paper,we propose and demonstrate a highly coherent frequency comb swept laser by using a high-quality(high-Q)microring comb filter to discretize a Fourier domain mode-locked(FDML)laser.The microring filter has a Q factor of^2×10^6 and a linewidth of^90 MHz.To demonstrate the improvement in performance,a Fabry-Perot comb filter with a Q factor of 6.2×10^4 and a linewidth of 3.1 GHz is also used in the experiment for comparison.Both comb filters have free spectral ranges(FSRs)of^50 GHz for consistence.Stable and clearly discretized temporal waveforms and frequency comb spectra with 50 GHz FSR are observed.Adoption of the high-Q microring filter narrows the instantaneous linewidth of the FDML laser down to 1.5 GHz.The OCT system with the frequency comb swept laser source with a microring filter demonstrates an ultralong imaging range,which has a 6,10,and 15 dB sensitivity roll-off length of^53,~73,and over 100 mm,respectively.