Time and Fourier domain jointly mode locked frequency comb swept fiber laser

Abstract

Fourier domain mode locked (FDML) fiber lasers enable megahertz wavelength sweeping rate but suffer from the short coherent length. Discretization of the swept spectrum by a comb filter was demonstrated effective to enhance the coherent length. In this paper, we propose a novel discretization method of the FDML signal with an intracavity intensity modulator. We propose and successfully demonstrate a time and Fourier domain jointly mode locked fiber laser with a Fabry-Perot comb filter and an intensity modulator in the cavity. A 50 GHz free spectral range comb filter in the Fourier domain mode locked fiber swept laser slices the spectrum into a series of comb lines and chops the swept signal into short pulses in time domain. The temporal signal is detected by a photodetector to generate a series of ultrashort pulses to drive the intensity modulator to further polish the intracavity pulses. We experimentally realized the proposed time and Fourier domain jointly mode locked fiber laser. Discrete wavelength swept laser output with a wavelength spacing of ~0.4 nm in a 41 nm sweeping range has been achieved.