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.

Polarization dynamics of dissipative soliton fiber laser

“…This trend is more apparent in a phase diagram for the ellipticity angle χ versus the spherical orientation angle ψ, which are calculated as follows Here, s1, s2, s3 are the stokes parameters of the laser SOP. At variance with the case of partial mode-locking [11], neither a bifurcation nor total turbulence can be identified here. As shown in Fig.…”

“…Typically, this behavior means that the proliferation time and decay time are the same, as it has been observed for the optical puff associated with the onset of optical turbulence [13]. The reason is that underlying physics of the two types of lasers are different: the evolution of the optical puff in a partially mode-locked fiber laser system is only associated with the presence of multiplemode-mixing [11,13]. Whereas the formation of an optical cluster in a dissipative fiber laser system is more complex, involving both nonlinearity, dispersion, filtering, and loss/gain.…”

Recent progress on optical rogue waves in fiber lasers: status, challenges, and perspectives

“…DFT has been used for observing the generation of RWs in the NLP regime. 82,[121][122][123][124] However, it is important to note that not all the NLPs could be considered as RWs. When the pulse-energy distribution of the NLPs is always Gaussian profile, this pulse state may be not the RW regime.…”

Coherence manipulation of partially mode-locked fiber laser

“…4). We inset a saturable absorber, which is fabricated by filling reduced graphene oxide flakes into cladding holes of a photonic crystal fiber, to detuning nonlinear phase for phase matching through adjusting the SOP of light.…”