title: Coherence loss of partially mode-locked fibre laser.
abstract: Stochastically driven nonlinear processes limit the number of amplified modes in a natural system due to competitive mode interaction, which is accompanied by loss of coherence when increasing the complexity of the system. Specifically, we find that modulation instability, which exhibits great fluctuations when it spontaneously grows from noise in conservative systems, may possess a high degree of coherence in dissipative laser system with gain. Nonlinear mode interactions can be competitive or cooperative: adjusting the intracavity polarization state controls the process of loss of coherence. Single-shot spectra reveal that, first, the fibre laser redistributes its energy from the center wavelength mode into sidebands through parametric instabilities. Subsequently, longitudinal modes are populated via cascaded four-wave-mixing. Parametric frequency conversion populates longitudinal modes with a random distribution of position, intensity and polarization, resulting in partially (rather than highly) coherent pulses. These dynamics unveil a new route towards complex pattern formation in nonlinear laser systems, and they may be also beneficial for the understanding of supercontinuum, Kerr-combs phenomena, and optical rogue waves.
authors.affiliation: Key Laboratory of Optoelectronic Technology &Systems (Ministry of Education), Chongqing University, Chongqing 400044, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Gao
authors.affiliation: Key Laboratory of Optoelectronic Technology &Systems (Ministry of Education), Chongqing University, Chongqing 400044, China.
authors.forename: Tao
authors.initials: T
authors.lastname: Zhu
authors.affiliation: Dipartimento di Ingegneria dell'Informazione, Università degli Studi di Brescia and INO-CNR, via Branze 38, 25123 Brescia, Italy.
authors.forename: Stefan
authors.initials: S
authors.lastname: Wabnitz
authors.affiliation: Key Laboratory of Optoelectronic Technology &Systems (Ministry of Education), Chongqing University, Chongqing 400044, China.
authors.forename: Min
authors.initials: M
authors.lastname: Liu
authors.affiliation: Key Laboratory of Optoelectronic Technology &Systems (Ministry of Education), Chongqing University, Chongqing 400044, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Huang