Self-gain-modulation random distributed feedback Raman fiber laser with switchable repetition rate.

We experimentally demonstrate a pulsed operation in a random fiber laser operation via self-gain-switching. The pulses have low timing jitter and high average output power. We show that repetition rate switches abruptly while varying the pump power, and introduce a simple formula for oscillation frequencies.

Random fiber laser based on a partial-reflection random fiber grating for high temperature sensing.

A stable single wavelength random fiber laser (RFL) with a partial-reflection random fiber grating (PR-RFG) for high temperature sensing is proposed and demonstrated for the first time, to the best of our knowledge. The PR-RFG is fabricated with the help of a femtosecond laser, with its highest reflection peak significantly higher than all other reflection peaks, which can ensure the stability of this filter-free RFL. Theoretical calculations also show that such a PR-RFG should be designed with reflectivity in the range of ∼30-90 to obtain one reflection peak significantly higher than other peaks.

Reflection of whispering gallery modes propagating on a surface of an optical fiber from its cleave.

We experimentally and numerically study the dynamics of whispering gallery modes slowly propagating within the cladding of an optical fiber near its end facet. We demonstrated that modes reflect from the fiber cleave. The reflection coefficient appears to reach 70% for the sample under study.

Nonlinear transition between PT-symmetric and PT-broken modes in coupled fiber lasers.

We present a systematic analysis of the stationary regimes of nonlinear parity-time (PT) symmetric laser composed of two coupled fiber cavities. We find that power-dependent nonlinear phase shifters broaden regions of existence of both PT-symmetric and PT-broken modes, and can facilitate transitions between modes of different types. We show the existence of non-stationary regimes and demonstrate an ambiguity of the transition process for some of the unstable states.

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.

SNAP microresonators introduced by strong bending of optical fibers.

We introduce a new method of the fabrication of surface nanoscale axial photonic (SNAP) microresonators through strong bending of an optical fiber. We experimentally demonstrate that geometric deformation and refractive index variation induced by bending is sufficient for the formation of a SNAP bottle resonator with nanoscale effective radius variation (ERV) along the fiber axis. In our experiment, we bend the optical fiber into a loop and investigate the properties of the fabricated tunable bottle resonator as a function of the loop dimensions.

Anderson localization in synthetic photonic lattice with random coupling.

A synthetic photonic lattice (SPL) is a re-configurable test-bed for studying the dynamics of one-dimensional mesh lattices including the photonic implementations of discrete time quantum walks. Unlike other realizations of photonic lattices, SPL possesses easy and fast control of lattice parameters. Here we consider disordered SPL where the coupling ratio between the two fiber loops realizing the lattice is random but does not change between the round trips.

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.

Self-Induced Faraday Instability Laser.

We predict the onset of self-induced parametric or Faraday instabilities in a laser, spontaneously caused by the presence of pump depletion, which leads to a periodic gain landscape for light propagating in the cavity. As a result of the instability, continuous wave oscillation becomes unstable even in the normal dispersion regime of the cavity, and a periodic train of pulses with ultrahigh repetition rate is generated. Application to the case of Raman fiber lasers is described, in good quantitative agreement between our conceptual analysis and numerical modeling.

Publisher Correction: Wave kinetics of random fibre lasers.

This corrects the article DOI: 10.1038/ncomms7214.

Generation of spatio-temporal extreme events in noise-like pulses NPE mode-locked fibre laser.

We experimentally study spatio-temporal generation of extreme events in the radiation of NPE mode-locked fibre laser generating noise-like pulses. We show that new pulses starts from high-intensity spatio-temporal structure which consist of mainly 3 subsequent pulses which are both separated over fast and slow evolution time. Statistical analysis of the noise-like pulse evolution over round-trips shows that the pulse width and intensity varies with a period of around 85 round-trips which does not change from pulse to pulse.

Anderson localization in synthetic photonic lattices.

Synthetic photonic lattices provide unique capabilities to realize theoretical concepts emerging in different fields of wave physics via the utilization of powerful photonic technologies. Here we observe experimentally Anderson localization for optical pulses in time domain, using a photonic mesh lattice composed of coupled fiber loops. We introduce a random potential through programmed electro-optic pulse phase modulation, and identify the localization features associated with varying degree of disorder.

Spectral correlations in a random distributed feedback fibre laser.

Random distributed feedback fibre lasers belong to the class of random lasers, where the feedback is provided by amplified Rayleigh scattering on sub-micron refractive index inhomogenities randomly distributed over the fibre length. Despite the elastic nature of Rayleigh scattering, the feedback mechanism has been insofar deemed incoherent, which corresponds to the commonly observed smooth generation spectra. Here, using a real-time spectral measurement technique based on a scanning Fabry-Pérot interferometer, we observe long-living narrowband components in the random fibre laser's spectrum.

Rogue waves generation via nonlinear soliton collision in multiple-soliton state of a mode-locked fiber laser.

We report for the first time, rogue waves generation in a mode-locked fiber laser that worked in multiple-soliton state in which hundreds of solitons occupied the whole laser cavity. Using real-time spatio-temporal intensity dynamics measurements, it is unveiled that nonlinear soliton collision accounts for the formation of rogue waves in this laser state. The nature of interactions between solitons are also discussed.

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.

Mode-locking via dissipative Faraday instability.

Emergence of coherent structures and patterns at the nonlinear stage of modulation instability of a uniform state is an inherent feature of many biological, physical and engineering systems. There are several well-studied classical modulation instabilities, such as Benjamin-Feir, Turing and Faraday instability, which play a critical role in the self-organization of energy and matter in non-equilibrium physical, chemical and biological systems. Here we experimentally demonstrate the dissipative Faraday instability induced by spatially periodic zig-zag modulation of a dissipative parameter of the system-spectrally dependent losses-achieving generation of temporal patterns and high-harmonic mode-locking in a fibre laser.

Laminar-Turbulent Transition in Raman Fiber Lasers: A First Passage Statistics Based Analysis.

Loss of coherence with increasing excitation amplitudes and spatial size modulation is a fundamental problem in designing Raman fiber lasers. While it is known that ramping up laser pump power increases the amplitude of stochastic excitations, such higher energy inputs can also lead to a transition from a linearly stable coherent laminar regime to a non-desirable disordered turbulent state. This report presents a new statistical methodology, based on first passage statistics, that classifies lasing regimes in Raman fiber lasers, thereby leading to a fast and highly accurate identification of a strong instability leading to a laminar-turbulent phase transition through a self-consistently defined order parameter.

Real-time high-resolution heterodyne-based measurements of spectral dynamics in fibre lasers.

Conventional tools for measurement of laser spectra (e.g. optical spectrum analysers) capture data averaged over a considerable time period.

Unveiling Temporal Correlations Characteristic of a Phase Transition in the Output Intensity of a Fiber Laser.

We use advanced statistical tools of time-series analysis to characterize the dynamical complexity of the transition to optical wave turbulence in a fiber laser. Ordinal analysis and the horizontal visibility graph applied to the experimentally measured laser output intensity reveal the presence of temporal correlations during the transition from the laminar to the turbulent lasing regimes. Both methods unveil coherent structures with well-defined time scales and strong correlations both, in the timing of the laser pulses and in their peak intensities.

Pattern Generation by Dissipative Parametric Instability.

Nonlinear instabilities are responsible for spontaneous pattern formation in a vast number of natural and engineered systems, ranging from biology to galaxy buildup. We propose a new instability mechanism leading to pattern formation in spatially extended nonlinear systems, which is based on a periodic antiphase modulation of spectrally dependent losses arranged in a zigzag way: an effective filtering is imposed at symmetrically located wave numbers k and -k in alternating order. The properties of the dissipative parametric instability differ from the features of both key classical concepts of modulation instabilities, i.

Graphene based widely-tunable and singly-polarized pulse generation with random fiber lasers.

Pulse generation often requires a stabilized cavity and its corresponding mode structure for initial phase-locking. Contrastingly, modeless cavity-free random lasers provide new possibilities for high quantum efficiency lasing that could potentially be widely tunable spectrally and temporally. Pulse generation in random lasers, however, has remained elusive since the discovery of modeless gain lasing.

Radiation build-up in laminar and turbulent regimes in quasi-CW Raman fiber laser.

We study the radiation build-up in laminar and turbulent generation regimes in quasi-CW Raman fiber laser. We found the resulted spectral shape and generation type is defined by the total spectral broadening/narrowing balance over laser cavity round-trip, which is substantially different in different regimes starting from first round-trips of the radiation build-up. In turbulent regime, the steady-state is reached only after a few round-trips, while in the laminar regime the laser approaches the equilibrium spectrum shape asymptotically.

Spatio-temporal generation regimes in quasi-CW Raman fiber lasers.

We present experimental measurements of intensity spatio-temporal dynamics in quasi-CW Raman fiber laser. Depending on the power, the laser operates in different spatio-temporal regimes varying from partial mode-locking near the generation threshold to almost stochastic radiation and a generation of short-lived pulses at high power. The transitions between the generation regimes are evident in intensity spatio-temporal dynamics.

Long-range and high-precision correlation optical time-domain reflectometry utilizing an all-fiber chaotic source.

We propose a long range, high precision optical time domain reflectometry (OTDR) based on an all-fiber supercontinuum source. The source simply consists of a CW pump laser with moderate power and a section of fiber, which has a zero dispersion wavelength near the laser's central wavelength. Spectrum and time domain properties of the source are investigated, showing that the source has great capability in nonlinear optics, such as correlation OTDR due to its ultra-wide-band chaotic behavior, and mm-scale spatial resolution is demonstrated.