Waveguides induced by photorefractive screening solitons

We study theoretically and experimentally the properties of waveguides induced by one-dimensional steady-state photorefractive screening solitons. We show that the number of possible guided modes in a waveguide induced by a bright soliton depends on the intensity ratio of the soliton, which is the ratio between the soliton peak intensity and the sum of the background illumination and the dark irradiance. We find that the number of guided modes increases monotonically with increasing intensity ratio. By adjusting the intensity ratio and the applied field, one can keep a fixed soliton size and at the same time vary the number of guided modes continuously. On the other hand, waveguides induced by dark screening solitons can support only one guided mode for all intensity ratios. Our experiments show good agreement with the theoretical results for both bright- and dark-soliton-induced waveguides.