We numerically demonstrate the existence of a discrete family of robust dissipative soliton bound state solutions ͑soliton molecules͒ in a mode-locked fiber laser with an instantaneous saturable absorber in the normal dispersion domain. For a certain domain of the small-signal gain, we obtain a robust first-level bound state with almost constant separation where the phase of the two pulses evolves independently. Moreover, their phase difference can evolve either periodically or chaotically depending on the small-signal gain. Interestingly, higher level bound states exhibit a fundamentally different dynamics. They represent oscillating solutions with a phase difference alternating between zero and. We identify the crucial role of the linear gain saturation for the existence of these robust molecules independently of their level.

We numerically investigate the formation of soliton pairs (bound states) in mode-locked fiber ring lasers. In the distributed model (complex cubic-quintic Ginzburg-Landau equation) we observe a discrete family of soliton pairs with equidistantly increasing peak separation. This family was identified by two alternative numerical schemes and the bound state instability was disclosed by a linear stability analysis. Moreover, similar families of unstable bound state solutions have been found in a more realistic lumped laser model with an idealized saturable absorber (instantaneous response). We show that a stabilization of these bound states can be achieved when the finite relaxation time of the saturable absorber is taken into account. The domain of stability can be controlled by varying this relaxation time.

We numerically demonstrate bistability of a robust dissipative soliton molecule with independently evolving phase in a normal dispersion mode-locked fiber laser. It is shown that the separation of the peaks exhibits a hysteretic behavior as a function of the pump energy. Physically this corresponds to the coexistence of two bound-state branches, one with chaotic dynamics and another one with periodic dynamics. The crucial role of gain saturation for the appearance of the hysteresis is revealed. We observe the period-doubling route to chaos.

Excimer and femtosecond lasers are widely used in ophthalmology to correct refraction. Laser systems for vision correction are based on versatile technical solutions and include multiple hard-and software components. Laser characteristics, properties of laser beam delivery system, algorithms for cornea treatment, and methods of pre-surgical diagnostics determine the surgical outcome. Here we describe the scientific and technological basis for laser systems for refractive surgery developed at the Physics Instrumentation Center (PIC) at the Prokhorov General Physics Institute (GPI), Russian Academy of Sciences.

The article analyzes elastic elements with a nonlinear characteristic. To improve the smoothness of a truck, a combined elastic element is proposed, including a semi-eleptic spring and an air cylinder, for installation in the rear axle suspension of a car. In order to assess the effect of a combined elastic element with a nonlinear characteristic on the smoothness of the ride, a mathematical model has been developed. The mathematical model allows for a numerical experiment taking into account the nature of the interaction of tires with unevenness of the roadway and the nonlinear characteristics of the combined elastic element.