Spontaneous one- and two-dimensional optical spatial solitons supported by photoisomerization nonlinearity in a bulk polymer

We present theoretically another type of optical spatial soliton in steady state, which is supported by photoisomerization nonlinearity in a polymer. For the photoisomerization nonlinearity with saturation, this type of one- or two-dimensional spatial soliton can be formed in a bulk polymer. The spontaneous soliton of this type can only be dark or gray. Not only a linearly polarized beam, but also a circularly polarized beam can be used to form the soliton, which is impossible for the photorefractive soliton. The effects of wavelength, polarization, and intensity of the beam on the formation of the soliton are discussed in detail.