Poisson distribution of extreme events in radiation of random distributed feedback fiber laser.

In the present Letter, we experimentally investigate extreme events in the time dynamics of the random distributed feedback fiber laser. We find that the probability of extreme events depends on the wavelength of the generated light. On spectrum tails, we register extreme events with intensity up to 50 times higher than the average generation power. Analysis of return times between successive rogue waves reveals their exponential distribution. Further investigation proves that the appearance of extreme waves in laser radiation obeys Poisson law. Characteristic radiation time varies from nanoseconds to tens of microseconds for most intense waves.

Spatial location of correlations in a random distributed feedback Raman fiber laser.

Nonlinear interactions between different components of multiwavelength radiation are one of the main processes shaping properties of quasi-CW fiber lasers. In random fiber lasers, nonlinear influence may be more complicated, as there are no distinct longitudinal modes in radiation because of the random nature of the feedback. In this Letter, we experimentally characterize internal correlations in the radiation of a multiwavelength random distributed feedback fiber laser. An analysis of Pearson correlation functions allows us to spatially locate the area over the fiber laser length in which correlations are more likely to occur. This, in turn, leads us to the conclusion about the main mechanism of spectral correlations-the relative intensity noise transfer from the pump wave.

Multi-peak structure of generation spectrum of random distributed feedback fiber Raman lasers.

We study spectral features of the generation of random distributed feedback fiber Raman laser arising from two-peak shape of the Raman gain spectral profile realized in the germanosilicate fibers. We demonstrate that number of peaks can be calculated using power balance model considering different subcomponents within each Stokes component.

Statistical properties of radiation of multiwavelength random DFB fiber laser.

In the presented paper, the temporal and statistical properties of a Lyot filter based multiwavelength random DFB fiber laser with a wide flat spectrum, consisting of individual lines, were investigated. It was shown that separate spectral lines forming the laser spectrum have mostly Gaussian statistics and so represent stochastic radiation, but at the same time the entire radiation is not fully stochastic. A simple model, taking into account phenomenological correlations of the lines' initial phases was established. Radiation structure in the experiment and simulation proved to be different, demanding interactions between different lines to be described via a NLSE-based model.

Frequency doubling of Raman fiber lasers with random distributed feedback.

This Letter presents what we believe is the first experimental study of frequency doubling of a Raman fiber laser (RFL) with random distributed feedback (RDFB) in an MgO:PPLN crystal. We compared two laser configurations, each with a half-open cavity. The cavity contained either a broadband Sagnac mirror or a narrowband fiber Bragg grating (FBG). We found that spectral broadening in the studied configurations of the RDFB RFLs differed from that found in a conventional RFL with a linear cavity, as well as from each other. We also compared the second harmonic generation (SHG) efficiency for these three types of lasers. The highest SHG efficiency was obtained for the RDFB RFL with the FBG delivering >100 mW power at 654 nm.

High-efficiency cascaded Raman fiber laser with random distributed feedback.

Cascaded lasing provided by Raman gain (at 1115-nm pumping) and random distributed feedback (via Rayleigh backscattering) in a 1.65-km phosphosilicate fiber is studied. Output power for the second Stokes component (1398 nm) exceeds 5 W at pump power of 11 W. In contrast to conventional cascaded Raman laser with high-Q cavity for the intermediate first Stokes component, there is no cavity here and no cavity losses, correspondingly. Longitudinal power distribution is shown to be quite different also. As a result, the efficiency of pump to 2nd Stokes wave conversion is not influenced by the intermediate stage and depends only on the integral attenuation in the fiber. Herewith, the number of generated 2nd Stokes photons at the output may even exceed the absorbed pump photons due to the lower attenuation of Stokes waves.

Publisher Correction: Wave kinetics of random fibre lasers.

This corrects the article DOI: 10.1038/ncomms7214.

Wave kinetics of random fibre lasers.

Traditional wave kinetics describes the slow evolution of systems with many degrees of freedom to equilibrium via numerous weak non-linear interactions and fails for very important class of dissipative (active) optical systems with cyclic gain and losses, such as lasers with non-linear intracavity dynamics. Here we introduce a conceptually new class of cyclic wave systems, characterized by non-uniform double-scale dynamics with strong periodic changes of the energy spectrum and slow evolution from cycle to cycle to a statistically steady state. Taking a practically important example-random fibre laser-we show that a model describing such a system is close to integrable non-linear Schrödinger equation and needs a new formalism of wave kinetics, developed here. We derive a non-linear kinetic theory of the laser spectrum, generalizing the seminal linear model of Schawlow and Townes. Experimental results agree with our theory. The work has implications for describing kinetics of cyclical systems beyond photonics.