Free-running mode-locked laser based dual-comb spectroscopy.

We present a real-time dual-comb spectrometer operated from a bidirectional mode-locked fiber laser in the wavelength range of 1.9 μm. Two pulsed signals emitted from a common cavity ensure mutual coherence and common mode noise rejection.

Bidirectional mode-locked thulium-doped fiber laser.

We report a bidirectional mode-locked thulium-doped fiber laser. Mode-locking is enabled by the combination of semiconductor saturable absorption and nonlinear polarization rotation. Two stable mode-locked picosecond pulse trains in opposite directions are generated with a fundamental repetition rate of ∼16.