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.

Reconfigurable time-stretched swept laser source with up to 100 MHz sweep rate,100 nm bandwidth,and 100 mm OCT imaging range

The sweep rate,sweep range,and coherence length of swept sources,respectively,determine the acquisition rate,axial resolution,and imaging range of optical coherence tomography(OCT).In this paper,we demonstrate a reconfigurable high-speed and broadband swept laser by time stretching of a flat spectrum femtosecond pulse train with over 100 nm bandwidth and a repetition rate of 100 MHz.By incorporating an optical modulator and utilizing appropriate dispersive modules,the reconfiguration of the swept source is demonstrated with sweep rates of 25 and 2.5 MHz.The 2.5 MHz swept source enables an imaging range of>110 mm with 6 dB sensitivity rolloff in OCT,which is the longest imaging range ever reported for megahertz OCT.