Passive mode-locking with slow saturable absorber: A delay differential model

We propose and study a new model describing passive mode-locking in a semiconductor laser - a set of differential equations with time delay. Analytical analysis of this model is performed under the slow saturable absorber approximation. Bifurcations responsible for the appearance and break-up of mode-locking regime are studied numerically

Strong synchronization of weakly interacting oscillons

We study interaction of well-separated oscillating localized structures (oscillons). We show that oscillons emit weakly decaying dispersive waves, which leads to formation of bound states due to subharmonic synchronization. We also show that in optical applications the Andronov-Hopf bifurcation of stationary localized structures leads to a drastic increase in their interaction strength

Chaotic bound state of localized structures in the complex Ginzburg--Landau equation

A new type of stable dynamic bound state of dissipative localized structures is found. It is characterized by chaotic oscillations of distance between the localized structures, their phase difference, and the center of mass velocity

A new model for passive mode-looking in a semiconductor laser

We propose a new model for passive mode-locking that is a set of ordinary delay differential equations. We assume the ring cavity geometry and a Lorentzian spectral filtering of the pulses, but do not use small gain and loss and weak saturation approximations. By means of a continuation method we study mode-locking solutions and their stability. We found that stable mode-locking can exist even when the non-lasing state between pulses becomes unstable

Chaotic soliton walk in periodically modulated media

We show that a weak transverse spatial modulation in (2+1) nonlinear Schrödinger equation with saturable nonlinearity can result in nontrivial dynamics of radially symmetric solitons. In particular, in the case of hexagonal profile of the modulation the soliton moves chaotically

Ab initio study of hydrogen in titanium beryllides

Titanium beryllide Be12Ti is a candidate material for the neutron multiplier for the demonstration fusion reactor DEMO. Experimental studies show that under certain conditions, Be12Ti may contain inclusions of other phases such as Be2Ti, Be17Ti2. In this regard, it is extremely important to study the diffusion of tritium and its isotopes in the crystal lattices of these phases. All calculations are performed using ab initio methods. Solution energies of a hydrogen atom in all non-equivalent interstitial sites of the three studied titanium beryllides were found to be lower than that in pure beryllium. The formation energy of all types of vacancies in all studied beryllides is found to be higher than that in beryllium. The binding energies of a single hydrogen atom located both inside and outside the vacancies are calculated. Hydrogen inside monovacancy is more strongly bound as compared to that outside this vacancy. It turned out that in some cases hydrogen can be captured by vacancy being outside of it. The results obtained can be useful for further study of interstitial diffusion of hydrogen and analysis of tritium retention in titanium beryllides

Modulational instability of discrete solitons in coupled waveguides with group velocity dispersion

We study temporal modulational instability of spatial discrete solitons in waveguide arrays with group velocity dispersion (GVD). For normal GVD we report existence of the strong 'neck'-type instability specific for the discrete solitons. For anomalous GVD the instability leads to formation of the mixed discrete-continuous spatio-temporal quasi-solitons. Feasibility of experimental observation of these effects in the arrays of silicon-on-insulator waveguides is discussed

Bifurcations in a model of monolithic passively mode-locked semiconductor laser

Operation regimes of a two section monolithic quantum dot mode-locked laser are studied theoretically using a model that takes into account carrier exchange between quantum dots and wetting layer. It is shown that when the absorber section length is large enough the laser exhibits bistability between laser off state and different mode-locking regimes. Q-switching instability leading to slow modulation of the mode-locked pulse peak intensity is completely eliminated in this case