[1] Jensen S M. The nonlinear coherent coupler. IEEE J. Quant. Electron., 1982, QE-18(10):1580～1583

[2] Finlayson N, Stegeman G I. Spatial switching, instabilities and chaos in a three-waveguide nonlinear directional coupler. Appl. Phys. Lett., 1990, 56(23): 2276～2278

[3] Sabini J P, Finlayson N, Stegeman G I. All-optical switching in nonlinear X junctions. Appl. Phys. Lett., 1989, 55(12): 1176～1178

[4] Leutheuser V, Langbein U, Lederer F. Optical response of a nonlinear bent directional coupler. Opt. Commun., 1990, 75(3,4): 251～255

[7] Liu G J, Liang B M, Li Q et al.. Multiple coupling length nonlinear directional couplers with variable coupling coefficient. Opt. Commun., 2003, 218(1): 113～117

[8] Hamid Hatami-Hanza, Chu P L. Shaping the switching characteristics of nonlinear directional couplers. Opt Commun., 1995, 119(3,4): 347～351