Interaction of dual-frequency pulses in passively mode-locked lasers (original) (raw)
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Continuous-wave versus pulse regime in a passively mode-locked laser with a fast saturable absorber
Journal of the Optical Society of America B, 2002
The phenomenon of modulation instability of continuous-wave (cw) solutions of the cubic-quintic complex Ginzburg-Landau equation is studied. It is shown that low-amplitude cw solutions are always unstable. For higher-amplitude cw solutions, there are regions of stability and regions where the cw solutions are modulationally unstable. It is found that there is an indirect relation between the stability of the soliton solutions and the modulation instability of the higher-amplitude cw solutions. However, there is no one-to-one correspondence between the two. We show that the evolution of modulationally unstable cw's depends on the system parameters.
Physical review. E, Statistical, nonlinear, and soft matter physics, 2001
The complex Ginzburg-Landau equation (CGLE) is a standard model for pulse generation in mode-locked lasers with fast saturable absorbers. We have found complicated pulsating behavior of solitons of the CGLE and regions of their existence in the five-dimensional parameter space. We have found zero-velocity, moving and exploding pulsating localized structures, period doubling (PD) of pulsations and the sequence of PD bifurcations. We have also found chaotic pulsating solitons. We have plotted regions of parameters of the CGLE where pulsating solutions exist. We also demonstrate the coexistence (bi- and multistability) of different types of pulsating solutions in certain regions of the parameter space of the CGLE.
Theory of passively mode-locked lasers for the case of a nonlinear complex-propagation coefficient
Journal of The Optical Society of America B-optical Physics, 1985
We examine passive mode locking, to which not only net-gain saturation but also group-velocity dispersion and self-phase modulation contribute significantly. Different sources of self-phase modulation are considered, and closed-form analytical solutions are obtained. The case of the colliding-pulse mode locking is discussed, and an ideal case is considered, in which the self-phase modulation and group-velocity dispersion are balanced so as to take maximum advantage of this additional shaping mechanism. This mechanism is shown to be similar to that which causes solitons in optical fibers; it provides additional reduction of the pulse width and significantly improves the stability against fluctuations in net gain.
Pulse Dynamics in an Actively Mode-Locked Laser
Siam Journal on Applied Dynamical Systems, 2003
We consider pulse formation dynamics in an actively mode-locked laser. We show that an amplitudemodulated laser is subject to large transient growth and we demonstrate that at threshold the transient growth is precisely the Petermann excess noise factor for a laser governed by a nonnormal operator. We also demonstrate an exact reduction from the governing PDEs to a low-dimensional system of ODEs for the parameters of an evolving pulse. A linearized version of these equations allows us to find analytical expressions for the transient growth below threshold. We also show that the nonlinear system collapses onto an appropriate fixed point, and thus in the absence of noise the ground-mode laser pulse is stable. We demonstrate numerically that, in the presence of a continuous noise source, however, the laser destabilizes and pulses are repeatedly created and annihilated.
Physical Review A, 2013
It has been shown by numerical simulation that the dissipative soliton resonance suppresses the appearance of new ultrashort pulses in the laser cavity that usually arise with increasing pumping. As a consequence, the energy of the pulses can reach an arbitrarily large value, which is determined by the corresponding pump power. The mechanism of the suppression is due to interaction between pulses through a saturable gain medium. The generation remains multistable: the number of pulses in steady-state operation depends on the initial conditions. In the case of multipulse generation, all pulses have identical durations, shapes, peak intensities, and chirps. The effect of maintaining single pulse operation with increasing pump power can be used to generate high-energy pulses.
Modeling of Mode-Locked Lasers
… of the 7th WSEAS International Conference …, 2007
Growing demand of communication networks requires ultra-short pulses. Ultra-short pulses can guarantee high data transfer and power. Fiber lasers, which are actively or passively mode-locked to generate ultrashort pulses, are termed as Mode locked fiber lasers. There are a number of methods available for mode-locking of lasers. We have discussed most of them in this paper. At the end a model of actively mode-locked fiber ring laser is simulated. Index terms: Active mode locking, Passive mode locking, Fiber lasers, Non-linear Schrodinger equation (NLSE), Saturable Absorber (SA).
Optics Communications, 1996
We present a method for simulating a passively mode locked laser. By selecting the simulation time step as the cavity round trip ti.me, we achieved a proper tracking of the temporal evolution of the individual cavity modes of the laser. Employing the split step Fourier algorithm using this natural modes base, an efficient simulation method was obtained, while retaining at each propagation step the direct physical relations between the calculated phase terms in the time and frequency domains to the actual optical field and individual cavity modes, respectively. Using this method, we tracked the formation of multiple pulses in a passively mode locked fiber laser cavity, and explored the effect of delayed optical feedback as a means for pulse ordering in fiber lasers.
Effects of cavity topology on the nonlinear dynamics of additive-pulse mode-locked lasers
Journal of the Optical Society of America B, 1998
We study the effect of cavity topology on the nonlinear dynamics of additive-pulse mode-locked (APM) lasers configured in the Fabry-Perot and Michelson geometries. In experiments the Fabry-Perot laser often exhibits such behaviors as period doubling and quasiperiodicity as the nonlinearity is increased, whereas the Michelson APM (M-APM) exhibits none of these effects. Numerical studies confirm that the M-APM appears to be more resistant to such behavior and thus is more tolerant to excessive nonlinearity in the control cavity. Using the concepts of intensity-and phase-dependent two-beam and multiple-beam interference, we obtain a general empirical rule connecting cavity topology to pulse train instabilities for fast saturable absorber modelocked lasers employing coupled cavities.
Multiple-Pulse Operation and Bound States of Solitons in Passive Mode-Locked Fiber Lasers
International Journal of …, 2011
We present results of our research on a multiple-pulse operation of passive mode-locked fiber lasers. The research has been performed on basis of numerical simulation. Multihysteresis dependence of both an intracavity energy and peak intensities of intracavity ultrashort pulses on pump power is found. It is shown that the change of a number of ultrashort pulses in a laser cavity can be realized by hard as well as soft regimes of an excitation and an annihilation of new solitons. Bound steady states of interacting solitons are studied for various mechanisms of nonlinear losses shaping ultrashort pulses. Possibility of coding of information on basis of soliton trains with various bonds between neighboring pulses is discussed. The role of dispersive wave emitted by solitons because of lumped intracavity elements in a formation of powerful soliton wings is analyzed. It is found that such powerful wings result in large bounding energies of interacting solitons in steady states. Various problems of a soliton interaction in passive mode-locked fiber lasers are discussed.
Physical Review A, 2012
On the basis of numerical simulation, it is found that powerful long-distance soliton wings can be formed by dispersive waves which are emitted by solitons because of lumped elements in a laser cavity. We analyze peculiarities of the interaction of two solitons through such wings in lasers with lumped saturable absorbers. Various sets of bound steady states of a two-soliton molecule are demonstrated. The relation between the spectral sidebands and the dispersive-wave wings of a soliton is found. The periodic changes in a soliton's profile during its pass through the laser cavity are studied.