Unidirectional, dual-comb lasing under multiple pulse formation mechanisms in a passively mode-locked fiber ring laser

TL;DR

This paper demonstrates a novel unidirectional dual-comb fiber laser that generates asynchronous ultrashort pulses with reduced noise, using multiple soliton formation mechanisms and a nanomaterial saturable absorber.

Contribution

It introduces a new dual-comb lasing scheme in a common-path, unidirectional fiber laser with multiple pulse formation mechanisms, enabling coherent dual-comb generation with simplified control.

Findings

Achieved simultaneous oscillation of pulses with different durations and repetition rates.

Verified coherence between picosecond and femtosecond pulses through spectroscopy.

Observed unusual bifurcation into two-pulse states due to soliton interactions.

Abstract

Dual-comb lasers from which asynchronous ultrashort pulses can be simultaneously generated have recently become an interesting research subject. They could be an intriguing alternative to the current dual-laser optical-frequency-comb source with highly sophisticated electronic control systems. If generated through a common light path traveled by all pulses, the common-mode noises between the spectral lines of different pulse trains could be significantly reduced. Therefore, coherent dual-comb generation from a completely common-path, unidirectional lasing cavity would be an interesting territory to explore. In this paper, we demonstrate such a dual-comb lasing scheme based on a nanomaterial saturable absorber with additional pulse narrowing and broadening mechanisms concurrently introduced into a mode-locked fiber laser. The interactions between multiple soliton formation mechanisms result in unusual bifurcation into two-pulse states with quite different characteristics. Simultaneous oscillation of pulses with four-fold difference in pulsewidths and tens of Hz repetition rate difference is observed. The coherence between these spectral-overlapped, picosecond and femtosecond pulses is further verified by the corresponding asynchronous cross-sampling and dual-comb spectroscopy measurements.