Temperature effects of dark solitons on the self-deflection of bright solitons in a separate bright-dark soliton pair

Abstract

Based on the theory of one-dimensional separate soliton pairs formed in a serial photorefractive crystal circuit, we investigated the temperature effects of the dark soliton on the self-deflection of the bright soliton in a bright-dark soliton pair. The numerical results obtained by solving the nonlinear propagation equation showed that the bright soliton moves on a parabolic trajectory in the crystal and its spatial shift changed with the temperature of the dark soliton. The higher the temperature of the dark soliton was, the smaller the spatial shift of the bright soliton was. The self-bending process was further studied by the perturbation technique, and the results were found to be in good agreement with that obtained by the numerical method.nonlinear optics, spatial optical solitons, photorefractive effects, self-deflection NONLINEAR OPTICS Spatial solitons in photorefractive (PR) media have aroused much interest in the past few years [1][2][3][4][5][6][7][8][9][10][11][12][13][14] . Up to date, three types of steady-state solitons, that is screening solitons [1,2] , photovoltaic (PV) solitons [3 -5] , and screening-photovoltaic solitons [6,7] , have been predicted and found experimentally [8][9][10] . At the same time, soliton pairs (coherent and incoherent) and soliton interaction have also been investigated [11][12][13][14][15] . However, the investigations on PR soliton, soliton pair and soliton interaction were concerned with only one piece of PR crystal [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] . Recently, a new type of soliton pair, named separate spatial soliton pair, which is formed in two PR crystals connected by electrode leads in a chain, was predicted by Liu et al. [16,17] , and the parametric coupling effects between the two solitons in a separate soliton pair were also studied in a serial photovoltaic-photorefractive crystal circuit [18] . These results indicate that the two solitons in a separate soliton pair depend on each other. Moreover, in the limit of the spatial extent of the optical wave being much less than the width of the crystal, changing the intensity of the dark soliton can affect the other soliton whereas the bright one cannot.Taking the diffusion effect into account, the bright soliton will deviate from its straight trajectory and bend during the soliton propagate in the photorefractive crystal, which is known as the self-deflection process [19][20][21] . The diffusion process and the dark irradiance of the crystal are both dependent on the temperature [22] . Therefore, temperature has an obvious effect on the self-deflection of bright solitons [23] . A natural question to address is whether the change of one crystal's temperature can affect the characteristics of another soliton in a separated spatial soliton pair. If it can, how can we control the self-deflection of one soliton by adjusting the