Discrete Fourier domain mode locked laser for simultaneous dual modal swept source OCT

In this paper, we propose and demonstrate a discrete Fourier domain mode locked (FDML) laser, which fully utilizes the high flexibility of temporal modulation. The FDML laser runs at the third harmonic frequency of the fiber cavity, which supports six independent swept signals in each cavity round trip. By manipulating the six swept signals, we demonstrate the ability to simultaneously generate multiple combinations of comb lines from a single FDML laser. The free spectral range (FSR) of each set of comb lines is 300 GHz but the six combs could be combined into combs with smaller FSRs. The discrete harmonic FDML laser enables a simultaneous dual modal swept source OCT with a fast imaging mode and a long imaging range mode obtained with the same set of data acquired. Such a swept source could also find applications in swept source LiDAR to realize interleaved line scanning.