Phase stabilization of an actively mode-locked ring laser

A phase-resolved system based on swept source optical coherence tomography (SS-OCT) has to incorporate a phase-stabilized wavelength-swept light source. The phase variation is induced by fluctuation of a beginning swept frequency. The conventional phase-sensitive SS-OCTs use a fiber Bragg grating (FBG) in order to avoid A-scan trigger fluctuations. However this method does not always solve the trigger fluctuation problem. In actively mode-locked ring lasers (AMLLs), the beginning swept frequency fluctuates by abrupt frequency change between the end of a sweep and the beginning of the subsequent one. To overcome this issue, we proposes a new phase stabilization method. By employing the method with an auxiliary reference configuration, the sweeping phase has successfully stabilized because the timing jitter is calculated by interference signals from the auxiliary reference path. In this research, we have proposed the phase stabilization method that has nanometer sensitivity with millisecond response. In addition, the method has successfully suppressed the depth dependence of phase instability.