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Fibre lasers display complex dynamical regimes which involve nonlinear interactions of millions of cavity modes. Recently, the transition to “optical turbulence” [1] (in analogy with the laminar-turbulence transition in hydrodynamic) was experimentally studied and was shown to be a phase transition which is accompanied by the occurrence of temporal correlations in the laser intensity with specific...
It was shown that the spectral width of a nominally continuous wave Raman fiber laser (RFL) output becomes narrower after propagation in normal dispersion (β2>0) fiber [1]. This feature, attributed to Inverse Four-Wave Mixing (IFWM), was especially pronounced when the RFL output had a double-peak spectral shape caused by efficient FWM inside the cavity [2]. This spectrum was transformed into a...
Photoacoustic microscopy (PAM) is a promising imaging modality that combines optical and ultrasound imaging. It combines the advantages of high ultrasonic spatial resolution and high optical contrast. When a short laser pulse illuminates the tissue, absorbed light leads to an acoustic emission via thermoelastic expansion [1]. The laser system needs to generate short enough pulses, i.e., several nanoseconds,...
Nonlinear Polarization Evolution (NPE) — a passive mode-locking technique — is successfully used in many all-fiber ultrafast oscillators. It is based on a temporal filtration of the pulse polarization state affected by a self-action due to the instantaneous Kerr nonlinearity. To work properly, most of NPE based architectures of fiber lasers contain pieces of standard optical fibers or bulk optical...
In the past years rare-earth-doped fiber lasers have emerged as attractive and power scalable solid-state laser concept due to the outstanding thermo-optical properties of an actively doped fiber. The large ratio of surface to active volume of such a fiber ensures excellent heat dissipation, furthermore the beam quality is defined by the refractive index profile of the active core and is therefore...
In the last few years several experimental and numerical results have been reported on the emergence of extreme events and instabilities in different laser configurations such as Raman fiber lasers, optically injected semiconductor lasers, laser diodes with optical feedback and mode-locked lasers [1-4]. Rogue events can however be expected in some of these systems due to the complex noise-driven processes...
Fiber and bulk lasers form two distinct classes of solid-state laser, both of which have achieved tremendous success in various arenas, but they are not without their limitations. The long, thin geometry of a fiber allows excellent heat dissipation, which combined with a waveguiding structure provides stronger resilience to thermally-induced mode distortions than in bulk lasers, allowing diffraction-limited...
Nonlinear optical frequency conversion in plasmonics has attracted immense research attention recently. Through various device geometries, harmonic generations of various orders have been reported. However, in these demonstrations, the near-field effect utilized has been limited to localized surface plasmons. It was not until last year that nonlinear frequency conversion utilizing propagating surface...
Probability distribution functions (PDF) with a tail longer than eight standard deviations are reflecting the presence of extreme processes in the system. Recently, we have shown that the cases of observation L-PDF need to be separated into two classes: the predictable events with L-PDF (PL-PDF) and the unpredictable (UL-PDF) ones. Also, it was observed that the case of oscillation system with seven...
The soliton — soliton interactions in mode-locked fiber lasers catch the attention of optical scientific society because it abounds in multifarious effects. As a sequence of these interactions (direct or indirect) the solitons constitute multi-soliton complexes with distinctive features. Bound solitons, bunch of solitons, and soliton rains have been widely covered in the literature, where were described...
Mechanisms of rogue waves (RWs) emergence have been extensively studied in fiber lasers with nonlinearly driven cavities [1], Raman fiber amplifiers and lasers [2], and fiber lasers via modulation of the pump [3]. Previously, it has been found that RWs can be emerged because of soliton-soliton interaction through the overlapping of their tails or soliton-dispersive wave interaction. The result of...
Statistically extreme events, that is to say, the events which have L-shaped probability distribution function (PDF, or in other words L-statistics) and, in particular, the rogue wave (RW) events, constitute a special family of natural phenomena. Curiously, this kind of events is more common than it is believed. It was observed that the behavior of the systems which obey L-shaped statistics is clustered...
Within recent years many ultra-short pulsed lasers with extremely high pulse energies as well as average powers were developed for laser material processing. To flexibly guide the beam from the laser to the workpiece hollow-core photonic crystal fibers (HC-PCF) have shown to be the best and unique choice to deliver these high peak power pulses. Also it has been reported that to largely reduce the...
A major advantage of solid-state lasers emitting in the 1 μm wavelength range is the possibility of using optical fibers for flexible beam delivery. This is already state of the art in laser material macro-processing with multimode beams. For modern high-brightness lasers with a diffraction-limited beam the guiding is restrained to a few meters or low powers due to nonlinear effects, mainly to Stimulated...
Bragg gratings were inscribed on the surface of thin GaN film grown on a sapphire substrate. These gratings are generated by illumination of 800 nm femtosecond pulses through a phase mask and a cylindrical lens.
Fiber lasers have come to a great prominence when it comes to stable high power and excellent beam quahty. They are used in industry for material processing, space apphcations as well as in medicine for precise surgery. Despite their widespread application they are not understood completely when it comes to longitudinal mode (LM) with stochastic phase relations and resulting nonlinear effects like...
π-shifted distributed feedback (DFB) fiber Bragg grating (FBG) Raman lasers have been demonstrated in the last few years [1, 2] and many attempts at optimisation have been made using theoretical calculations [3]. However, due to the limitations of resolution of the coupled-mode equations, theoretical optimisation has been limited to a few case studies. By using a simple approximation, we demonstrate...
Raman fiber lasers (RFLs) are treated as perspective laser sources in spectral bands which are not available from rare-earth (RE) doped fiber lasers. Raman lasing can be easily obtained from 1.1 to 2 μm in single-mode fibers that are core-pumped by RE-doped fiber lasers generating single transverse mode. However, the RFL generation below 1, Mm is difficult because of a lack of suitable high-power...
High power linearly polarized narrow linewidth light source above the wavelength of 1600 nm are very attractive for several applications such as pump source for Cr:ZnS[1], Tm:Re2O3 (Re=Sc. Lu or Y) or nonlinear frequency conversion. Er (or Er:Yb)fibers are most popular gain media around the wavelength of 1.55 μm, though, there are few reports of Er fiber lasers above 1600 nm satisfying aforementioned...
Advances in the research fields of biological, biophysical and biochemistry rely on the development of novel, flexible, powerful and reliable laser sources in the visible — NIR part of the spectrum [1, 2]. Optical excitation in the 750–800 nm region, with flexible pulsed formats, can be advantageous in applications such as confocal fluorescence microscopy, STED, FLIM microscopy, photoluminescence...
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