Studies On All-Optical Control Based On Nonlocality

With the development of electronic technology, electronic technologies have reached several bottlenecks in some fields. One of the methods to deal with this problem is to combine optical technology and electronic technology. So, the studies on nonlinear optical materials and optical controlling is important. In recent decades, optical spatial soliton is a hot research topic in optical field, the relevant results may be applied in several aspects such as all-optical switch and controlling.Based on the nonlinear Schrodinger equation and Poisson equation, the properties of optical beam during its transmission in the media are studied in detail by employing numerical simulation method. First, the nonlocal nonlinear Schrodinger equation is solved, and its solution is obtained. Next, we studied the dynamical properties of the beam when it propagates in the thermal nonlinear medium. Finally, the possibility of applications of these properties to all-optical controlling is also discussed.The main contents are as follows:(1) The properties of localized optical field, which existed in the thermal nonlinear medium, are studied in detail. By combining Fourier method with the LU decomposition method, the steady-state mode which existed in the thermal nonlinear medium, is obtained. We investigated the influence of nonlinear coefficience and energy flow on optical field and temperature distributions. The results show:the bigger the nonlinear coefficient, the greater the peak values of optical field amplitude and temperature; meanwhile, the smaller the width of the beam. With an increase of energy flow, the peak values of optical field amplitude and temperature increases, and the beam width decreases. The effect of calculation window on the steady-state mode and temperature distributions is also presented, and we find that calculation window can’t change the distribution of optical field and the shape of temperature distribution.(2) The influence of linear refractive index distributions on the steady-state optical field in the thermal nonlinear medium is investigated. For cosine lattices, several parameter, such as lattice depth, lattice frequency and nonlinear coefficient, have remarkable influence on the steady-state optical field. Under the circumstance of step-index distribution, it makes the beam center deviate from the surface.(3) We also consider the dynamical properties of the beam during its propagation in thermal nonlinear medium with optical lattices. For cosine lattices, after withdrawing it, propagation trajectories of optical beam don’t change, however, the breathing behavior occurs. Conversely, for the step-index distribution, the results will be much different, it make the beam vibrate in a transverse direction.(4) Existence and stability of the fundamental and higher-order solitons, which exist in nonlinear media with asymmetric response and periodic linear refractive index modulation, are presented. It is found that the existence of solitons results in the balance between linear refractive index modulation (optical lattices) and nonlinear refractive index induced by incident optical field. In addition, Dynamical properties of fundamental mode solitons are also investigated in detail, and may be applied in the fields of soliton controlling and steering.