Dissipative soliton resonance (DSR) is an efficient way to achieve high energetic pulses without wave breaking. In fiber laser, DSR operation manifests as square pulses emission. Based on this principle, we have experimentally demonstrated pulses in the micro joule range. Experiments have been conducted using double-clad Er:Yb-doped fiber lasers in different optical configurations. In particular, we demonstrate 10 μJ DSR emission in an optimized cavity and also the possibility to observe wave breaking in DSR regime. In the latter case, harmonic mode-locking of square pulses is demonstrated.
The effect of an external continuous wave (cw) on the operating regime of a passively mode-locked double-clad fiber
laser, operating in the anomalous dispersion regime, is experimentally investigated. Starting from different soliton
distributions, we demonstrate that, under specific conditions, the cw signal forces the principal laser to operate in
harmonic mode-locking regime.
Ordered and disordered pattern formation of solitons is experimentally investigated in the passively mode-locked doubleclad
erbium-doped fiber laser. Soliton complexes of about 500 pulses are obtained which organize in different patterns
analogous the states of the matter. We have identified a soliton gas, a supersonic soliton gas flow, a soliton liquid, a
soliton polycrystal and a crystal of solitons.
We report on the observation of bound state of some hundreds of solitons in a passively mode-locked Er:Yb-doped fiber
laser. A double-clad fiber is used in a unidirectional ring cavity where the mode-locking is obtained thanks to the
nonlinear polarization rotation. The phenomenon is described theoretically using a multiscale approach to the gain dynamics.
The interaction of dissipative solitons in fiber laser with nonlinear losses due to nonlinear polarization rotation is studied
by numerical simulation. Technique control of spectrum and amplitude of pulse wings allows effective management of
the soliton interaction under long distance between pulses (considerably much more than pulse duration). The interaction
can be attractive or repulsive. Moreover the sign of the interaction may depend on distance between pulses.
The multiple pulse passive mode-locking with equidistantly arranged pulses in a laser cavity has been analyzed.
Mechanisms resulting in such type of passive mode-locking have been studied. Among of them there are the additional
weak active amplitude and phase modulations of the intracavity radiation, the additional inertial nonlinear refractive
index and darkening absorber. The transient period for the realization ofthe harmonic passive mode-locking due to these
mechanisms has been estimated.
We present the results of our theoretical investigation on passive mode-locking of fiber lasers. The mode-locking is achieved using the nonlinear polarization technique. The practical case of the ytterbium-doped fiber laser operating is analysed. A simple model is developed allowing to study several features observed in passively mode-locked fiber lasers such as bistability between the mode-lock and the continuous regime, multiple pulse operation, hysteresis phenomena, bound solitons. The dynamics of the number of pulses as a function of laser parameters is also reported. Pump power hysteresis is demonstrated.
We present the results of our investigation on the spectral dynamics of dissipative solitons in passive mode-locked lasers with non-instantaneous saturable absorbers. Mechanisms for temporal periodically repeated drift of carrier frequency and for chaotic temporal changes in spectrum of ultrashort pulses have been established. These results are applicable to communication fiber lines with non-instantaneous saturable absorbers.
We study generation regimes of passive mode-locked lasers with nonlinear and dispersive parameters dependent on characteristics of resulting pulses. It is shown that such dependence can cause pulse splitting, multiple pulse operation, multistability, hysteresis phenomena, bistability between cw operation and passive mode-locking. Obtained results are compared with experimental data.
A novel approach for the stabilization of soliton sequences in fibers with an amplification and a saturable absorption is put forward. The instability related with a merge of solitons is suppressed by their frequency chirp due to nonlinear refractive index. Weak noise pulses connected with an amplified spontaneous emission are suppressed by a saturable absorption. Powerful solitons with different amplitudes are equalized by negative feedback, which is due to the combined action of a nonlinear refractive index inducing a frequency chirp of solitons and of a frequency dispersion of a gain-loss. The application of obtained results on the stabilization of soliton sequences to optical communications and information processing is discussed.
The propagation and the stability of sequences of dissipative solitons in fibers with gain, saturable absorption, and spectral band limitation of radiation has been analysed. The spectrum dependence for a gain is approximated by a squared frequency dispersion. The spectrum-dependent loss related with the additional spectral limitatiaon is modeled by a fourth order frequency one. It is found that the combined action of the nonlinear refractive index inducing a frequency soliton chirp and of the indicated spectral limitation causes the negative feedback. By the action of this negative feedback and the positive feedback due to saturable absorption on propagating pulses, the dissipative soliton sequences is stabilized: the weak noise pulses are suppressed, the powerful signal solitons with different amplitudes are equalized. The found stabilization can present interest for a management of sequences of dissipative solitons in fiber lines.
Novel mechanisms resulting in generation bistability of passive mode-locked lasers is predicted. It is shown by numerical simulation that after transient evolution either stationary single pulse operation or operation in which the whole laser cavity is filled with the generated radiation can be realized depending on the initial conditions. This bistability is connected with the phase-modulation instability of passive mode-locking in circumstances where the spectral gain-loss profile has a complicated from. The complicated profile can be related to a spectral selectivity of parasitic losses or to a spectral selectivity of parasitic losses or to a spectral inhomogeneity of an active medium amplification. The assumed manifestations of this mechanism in actual experimental systems are discussed.
Numerical simulation of ultrashort pulse generation in the laser with a composite active medium and additional Raman active element in a cavity has been done. It was created that for some laser parameters the optimization of a Raman gain and a frequency shift values was resulted in additional shortening of pulse duration.
The propagation and the evolution of dissipative solitons in fibers with a gain and a saturable absorption are investigated. It is shown that the combined action of a nonlinear refractive index resulting in frequency chirp of pulses and of a frequency dispersion of gain induces the negative feedback. As a result, the sequence of dissipative solitons is stabilized: the weak pules are suppressed, the powerful pulses with different amplitudes are equalized.
One of the possible methods of realization of active medium with anomalously wide bandwidth has been described. Composite active medium, consisting of several laser active centers with overlapping gainbands in common resonator has been created. In this case gain contour has complex shape with local extremums. Method of numerical simulation of the formation dynamics of ultrashort pulse at passive mode locking in laser with arbitrary spectral gain contour has been performed. The main parameters for the generation of ultrashort pulse in a laser with a composite active medium are obtained and investigated. The conditions of realization of stationary regime in the form of ultrashort pulse generation with duration determined by combined gain bandwidth are calculated.
Multiple pulse operation of passive mode-locked lasers with nonlinear refractive index of intracavity elements has been investigated. The hysteresis dependence of number of pulses in established regime on the pump power has been found. It is shown that this number depends also on initial condition of generation. The application of discovered multistability and hysteresis to optical communications and information processing is discussed.
Nonlinear dynamics due to the phase modulation instability and resulting in the bistability for the regime of formation of ultrashort pulses is investigated. We studied the regime of breathing ultrashort pulse due to this instability. Other possible established regime connects with an increase in the number of stable stationary ultrashort pulses in laser cavity. It is shown that type of established regime depends on initial conditions.