[1] Singh S R, Christodoulides D N. Evolution of spatial optical solitons in biased photorefractive media under steady state conditions [J]. Opt. Comm., 1995, 118: 569-576.

[2] Christodoulides D N , Carvalho M I. Bright, dark and gray spatial soliton states in photorefvactive media [J]. J. Opt. Soc. Am. B, 1995, 12(9): 1628-1633.

[3] Segev M, Vally G C, Bashaw M C, et al. Photovoltaic spatial solitons [J]. J. Opt. Soc. Am. B, 1997, 14(7): 1772-1781.

[4] Duree G C, Shultz J L, Salamos G J, et al. Observatiom of self-trapping of an optical beam due to the photorefractive effect [J]. Phys. Rev. Lett., 1993, 71(4): 533-536.

[5] Liu Jinsong, Lu Keqing. Screening-photovoltaic spatial solitons in biased photovoltaic-photorefractive crystals and their self-deflection [J]. J. Opt. Soc. Am. B, 1999, 16(4): 550-555.

[9] Shih M F, Chen Z G, Segev M, et al. Incoherent collisions between one-dimensional bright steady-state photorefractive spatial screening solitons [J]. Appl. Phys. Lett., 1996, 69(27): 4151-4153.

[10] Shih M F, Segev M. Incoherent collisions between two-dimensional bright steady-state photorefractive spatial screening solitons [J]. Opt. Lett., 1996, 21(19): 1538-1540.

[11] Stepken A, Kaiser F, Belic M R, et al. Interaction of incoherent two-dimensional photorefractive solitons [J]. Phys. Rev. E, 1998, 58(4): R4112-4115.

[13] Castro Camus E, Magana L F. Prediction of the physical response for the two-photon photorefractive effect [J]. Opt. Lett., 2003, 28, 1129-1131.

[14] Hou Chunfeng, Pei Yanbo, Zhou Zhongxiang, et al. Spatial solitons in two-photon photorefractive media [J]. Phys. Rev. A, 2005, 71: 053817.

[15] Hou Chunfeng, Zhang Yu, Jiang Yongyuan, et al. Photovoltaic solitons in two-photon photorefractive materials under open-circuit conditions [J]. Opt. Commun., 2007, 273: 544-548.

[16] Zhang Yu, Hou Chunfeng, Sun Xiaodong. Grey spatial solitons due to two-photon photorefractive effect [J]. Chin. Phys., 2007, 16(1): 159-164.

[18] Zhang Guangyong, Liu Jinsong. Screening-photovoltaic spatial solitons in biased two-photon photovoltaic photorefractive crystals [J]. J. Opt. Soc. Am. B, 2009, 26(1): 113-120.