Sergey K. Turitsyn

Generation of double-scale femto/pico-second optical lumps in mode-locked fiber lasers

We observed generation of stable picoseconds pulse train and double-scale optical lumps with picosecond envelope and femtosecond noise-like oscillations in the same Yb-doped fiber laser with all-positive-dispersion cavity mode-locked due to the effect of non-linear polarization evolution. In the noise-like pulse generation regime the auto-correlation function has a non-usual double (femto- and picosecond) scale shape. We discuss mechanisms of laser switching between two operation regimes and demonstrate a good qualitative agreement between experimental results and numerical modeling based on modified nonlinear Schrödinger equations.

Nonlinear modes of a macroscopic quantum oscillator

Abstract We consider the Bose–Einstein condensate in a parabolic trap as a macroscopic quantum oscillator and describe, analytically and numerically, its collective modes — a nonlinear generalisation of the (symmetric and antisymmetric) Hermite–Gauss eigenmodes of a harmonic quantum oscillator.

Waveguide-saturable absorber fabricated by femtosecond pulses in YAG:Cr4+ crystal for Q-switched operation of Yb-fiber laser

A waveguide-saturable absorber with low propagation loss is fabricated by femtosecond pulses in YAG:Cr(4+) crystal. Q-switch operation of a Yb fiber laser with the new saturable absorber having absorption saturation parameters similar to the bulk YAG:Cr(4+) crystal is demonstrated.

Modulation instability in high power laser amplifiers

The modulation instability (MI) is one of the main factors responsible for the degradation of beam quality in high-power laser systems. The so-called B-integral restriction is commonly used as the criteria for MI control in passive optics devices. For amplifiers the adiabatic model, assuming locally the Bespalov-Talanov expression for MI growth, is commonly used to estimate the destructive impact of the instability. We present here the exact solution of MI development in amplifiers. We determine the parameters which control the effect of MI in amplifiers and calculate the MI growth rate as a function of those parameters. The safety range of operational parameters is presented. The results of the exact calculations are compared with the adiabatic model, and the range of validity of the latest is determined. We demonstrate that for practical situations the adiabatic approximation noticeably overestimates MI. The additional margin of laser system design is quantified.

Higher-Order Soliton Generation in Hybrid Mode-Locked Thulium-Doped Fiber Ring Laser

A thulium-doped all-fiber laser passively mode-locked by the co-action of nonlinear polarization evolution and single-walled carbon nanotubes operating at 1860-1980 nm wavelength band is demonstrated. Pumped with the single-mode laser diode at 1.55 μm laser generates near 500-fs soliton pulses at repetition rate ranging from 6.3 to 72.5 MHz in single-pulse operation regime. Having 3-m long cavity average output power reached 300 mW, giving the peak power of 4.88 kW and the pulse energy of 2.93 nJ with slope efficiency higher than 30%. At a 21.6-m long ring cavity average output power of 117 mW is obtained, corresponding to the pulse energy up to 10.87 nJ and a pulse peak power of 21.7 kW, leading to the higher-order soliton generation.

On-off and multistate intermittencies in cascaded random distributed feedback fibre laser

The paper studies intensity fluctuations in a random DFB fiber laser based on nitrogen doped fiber. The laser generates first and second Stokes components 1120 nm and 1180 nm respectively under an appropriate pumping. This work studies the intermittency in the radiation of the second Stokes wave.

Digital back propagation in soliton coherent transmission

We have revised soliton transmission in the new context of coherent optical detection optimizing and comparing digital backward propagation and in-line optical filtering as a means to suppress soliton timing and phase jitter. We find that in-line optical filtering allows one to improve the reach of the soliton system by up to the factor of two. We compared jitter suppression for transmission links using different types of fiber. We showed that with launch power growth jitter suppression is less efficient. However, our results show that nonlinear propagation can lead to enhanced performance of the fiber network systems.

Raman gain and random distributed feedback generation in nitrogen doped silica core fiber

Recently, the concept of a random distributed feedback (DFB) lasing in optical fibers has been demonstrated [1], A number of different random DFB fiber lasers has been demonstrated so far including tunable, multiwalength, cascaded generation, generation in different spectral bands etc [2-7]. All systems are based on standard low-loss germanium doped silica core fibres having relatively low Rayleigh scattering coefficient. Thus, the typical length of random DFB fiber lasers is in the range from several kilometres to tens of kilometres to accumulate enough random feedback. Here we demonstrate for the first time to our knowledge the random DFB fiber laser based on a nitrogen doped silica core (N-doped) fiber. The fiber has several times higher Rayleigh scattering coefficient compared to standard telecommunication fibres. Thus, the generation is achieved in 500 meters long fiber only.

Migration from Periodic to Lumped Dispersion Mapping in Existing SMF/DCF Links

The aim of this work is to study the effects of concentrating the dispersion compensation modules (DCMs) at specific points along the dispersion map -lumped mapping, as opposite to deploying a larger number of smaller (DCMs) placed periodically along the map. System setup and numerical modelling are given also in detail.

On the mutual interaction of self-focusing and stimulated scattering☆

Abstract The interaction of the light self-focusing and stimulated Brillouin scattering (SBS) in a nonlinear medium is considered. We demonstrate that SBS seeded from the rear surface of the medium can suppress the self-focusing. As a result, a power much larger than the critical one can be transmitted through the crystal. The self-focusing suppression results in enhanced SBS and a transversal laser beam structure modification.