Ndifon Ngek

Femtosecond laser inscription in transparent materials is a physical process that finds widespread applications in material engineering, particularly in laser micromachining technology. In this process, the nonlinear optical response of the transparent material can be either intrinsic or induced by multiphoton ionization processes. In this work, a generic model is considered to describe the dynamics of femtosecond laser filamentation in transparent materials characterized by non-Kerr nonlinearities, focusing on the influence of multiphoton ionization processes in the generation of an electron plasma of inhomogeneous density. The mathematical model consists of a complex Ginzburg–Landau equation with a generalized saturable nonlinearity, besides the residual nonlinearity related to multiphoton ionization processes. This generalized complex Ginzburg–Landau equation is coupled to a rate equation for time evolution of the electron plasma density, where multiphoton ionizations are assumed...

The influence of thermo-optic effects on shape profiles of soliton crystals in optical Kerr microresonators is investigated. The study rests on a model that consists of the Lugiato–Lefever equation, coupled to the one-dimensional heat diffusion equation with a source term proportional to the average power of the optical field. Using appropriate variable changes the model equations are transformed into a set of coupled first-order nonlinear ordinary differential equations. These equations are solved numerically with emphasis on the influence of thermo-optic effects on the amplitude and instantaneous frequency of the optical field, as well as on the temperature profile in the microresonator cavity. It is found that thermo-optic effects do not prevent soliton crystals from forming in optical Kerr microresonators, however, a strong thermal detuning will decrease the soliton-crystal amplitude. The model predicts a temperature profile in the microresonator cavity which is insensitive to t...

Exciton–polariton solitons are nonlinear quasiparticles composed of exciton–photon bound states due to the interaction of light with matter. In semiconductor micro-cavity systems, such as semiconductor micro and nanowires, polaritons are characterized by a negative mass which, combined with the repulsive nonlinear exciton–exciton interaction, leads to the generation of bright polariton solitons. In this work, we investigate the dynamics of bright exciton–polariton solitons in a finite-sized microcavity waveguide, assuming radiative losses to be balanced by the external pumping. Bright-soliton solutions to the model equations of motion, which consist of a periodic train of polariton pulses, are obtained in terms of Jacobi elliptic functions. Analytical expressions of the energies of both photonic and excitonic components of the pulse train are found. Results suggest that the size of a nanowire waveguide plays a relevant role in the quantitative estimate of the energy conveyed by pola...

Femtosecond laser inscription in transparent materials is a physical process that finds widespread applications in material engineering, particularly in laser micromachining technology. In this process, the nonlinear optical response of the transparent material can be either intrinsic or induced by multiphoton ionization processes. In this work, a generic model is considered to describe the dynamics of femtosecond laser filamentation in transparent materials characterized by non-Kerr nonlinearities, focusing on the influence of multiphoton ionization processes in the generation of an electron plasma of inhomogeneous density. The mathematical model consists of a complex Ginzburg–Landau equation with a generalized saturable nonlinearity, besides the residual nonlinearity related to multiphoton ionization processes. This generalized complex Ginzburg–Landau equation is coupled to a rate equation for time evolution of the electron plasma density, where multiphoton ionizations are assumed...

The influence of thermo-optic effects on shape profiles of soliton crystals in optical Kerr microresonators is investigated. The study rests on a model that consists of the Lugiato–Lefever equation, coupled to the one-dimensional heat diffusion equation with a source term proportional to the average power of the optical field. Using appropriate variable changes the model equations are transformed into a set of coupled first-order nonlinear ordinary differential equations. These equations are solved numerically with emphasis on the influence of thermo-optic effects on the amplitude and instantaneous frequency of the optical field, as well as on the temperature profile in the microresonator cavity. It is found that thermo-optic effects do not prevent soliton crystals from forming in optical Kerr microresonators, however, a strong thermal detuning will decrease the soliton-crystal amplitude. The model predicts a temperature profile in the microresonator cavity which is insensitive to t...

Exciton–polariton solitons are nonlinear quasiparticles composed of exciton–photon bound states due to the interaction of light with matter. In semiconductor micro-cavity systems, such as semiconductor micro and nanowires, polaritons are characterized by a negative mass which, combined with the repulsive nonlinear exciton–exciton interaction, leads to the generation of bright polariton solitons. In this work, we investigate the dynamics of bright exciton–polariton solitons in a finite-sized microcavity waveguide, assuming radiative losses to be balanced by the external pumping. Bright-soliton solutions to the model equations of motion, which consist of a periodic train of polariton pulses, are obtained in terms of Jacobi elliptic functions. Analytical expressions of the energies of both photonic and excitonic components of the pulse train are found. Results suggest that the size of a nanowire waveguide plays a relevant role in the quantitative estimate of the energy conveyed by pola...

A theoretical scheme for an experimental implementation involving bisolitonic matter waves from an attractive Bose–Einstein condensate, is considered within the framework of a non-perturbative approach to the associate Gross–Pitaevskii equation. The model consists of a single condensate subjected to an expulsive harmonic potential creating a double-condensate structure, and a gravitational potential that induces atomic exchanges between the two overlapping post condensates. Using a non-isospectral scattering transform method, exact expressions for the bright-matter–wave bisolitons are found in terms of double-lump envelopes with the co-propagating pulses displaying more or less pronounced differences in their widths and tails depending on the mass of atoms composing the condensate.