Laser dynamics in nonlinear transparent media with electron plasma generation: effects of electron–hole radiative recombinations

Abstract

The performance of optical devices manufactured via laser micromachining on nonlinear transparent materials usually relies on three main factors, which are the characteristic laser parameters (i.e. the laser power, pulse duration and pulse repetition rate), the characteristic properties of host materials (e.g. their chromatic dispersions, optical nonlinearities or self-focusing features) and the relative importance of physical processes such as the avalanche impact ionization, multiphoton ionization and electron–hole radiative recombination processes. These factors act in conjunction to impose the regime of laser operation; in particular, their competition determines the appropriate laser operation regime. In this work a theoretical study is proposed to explore the effects of the competition between multiphoton absorption, plasma ionization and electron–hole radiative recombination processes on the laser dynamics in transparent materials with Kerr nonlinearity. The study rests on a model consisting of a K-order nonlinear complex Ginzburg–Landau equation, coupled to a first-order equation describing time variation of the electron plasma density. An analysis of the stability of continuous waves, following the modulational instability approach, reveals that the combination of multiphoton absorption and electron–hole radiative recombination processes can be detrimental or favorable to continuous-wave operation, depending on the group-velocity dispersion of the host medium. Numerical simulations of the model equations in the fully nonlinear regime reveal the existence of pulse trains, the amplitudes of which are enhanced by the radiative recombination processes. Numerical results for the density of the induced electron plasma feature two distinct regimes of time evolution, depending on the strength of the electron–hole radiative recombination processes.

Self-starting dynamics of continuous-waves stability in a generalized complex nonlinear transparent media for passively mode-locked lasers with fast saturable absorbers

“…This means that the noise amplitudes in this case are constant and therefore the cw regime is expected to be always stable. this is consistent with the result found in [35]. Thus for k 2 > 0, satisfies laser self-starting mode regime, which is interpreted mathematically as follows:…”

“…The minus sign at P 2 in equation (7) came from the fact that the saturable absorber effect represent the optical absorption loss. When this laser saturation power (P 2 )(power level required for achieving significant saturation of an absorber or a gain medium) goes to zero, our result is consistent with that found in [35]. To be more precised, given that equation (1) described the fact that multiphoton absorption processes will reduce or increase the threshold value of the input power needed for the laser to operate in the cw regime [36,37], depending on the characteristic values parameters of the model.…”

“…It is clearly seeing that the input laser field intensity is a function of the number of K-photon absorption in the medium. When Γ = 0, the model above reduces to the case examined by Kameni Nteutse et al [35]. Whereas, when considering very small values of Γ, the last term to the right hand side of equation (1) after expansion, will yield a given others of Complex Ginzburg-Landau equation with high order nonlinearities [37][38][39][40][41].…”

Soliton crystals in optical Kerr microresonators in the presence of thermo-optic effects

“…This latter equation is characterized by two parameters namely A and B, assumed to control temperature variation in the microresonator cavity during the optical field roundtrips, as well as a source term proportional to the average power of the optical field within the cavity. By solving numerically the model equations assuming a specific ansatz [27][28][29][30][31] for the optical field, we found that an increase of the characteristic parameter A with B fixed favours an increase of the amplitude of dissipative soliton crystals. We noted that the temperature profile was not influenced by characteristic parameters in the optical-field equation, but only by those involved in the heat equation.…”

Dynamics and stability of ultrashort laser in Kerr nonlinear optical materials: competing effects between K-photon absorption and the higher-order correction term to the nonlinear refractive index

“…However, nonlinear solutions (i.e. pulse) only exist for specific values of v and ω [18,20,28]. Therefore we will only pay attention to the case of zero-velocity solutions (i.e.…”