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(Color online) Frequency vs Bloch vector of the first band along direction. The solid, upper dashed and lower dashed lines are the cases, without nonlinearity, with the tuned smaller and larger, respectively. The SC point for each case is marked by , , and . Inset (a) shows the EFCs of the first band in space without nonlinearity. The red line represents the EFC of SC. In the inset (b), the divergent, SC and convergent behaviors of beam propagation are schematically shown by the group velocity vectors for EFCs with negative, zero, and positive curvatures, respectively.
(Color online) (a) Field vs of stable beams in the nonlinear PhC of (upper panel) (weak nonlinearity) and (lower panel) (the tunable SC is achieved), where is the peak amplitude of the Gaussian beam. The thick black lines represent the detection area. (b) The divergence angle vs the incident field , where the divergence angle is defined as . is the distance from the source to the detection plane; is the change of the beam half-width on the detecting plane. .
(Color online) Beamwidth vs the beam propagating distance. The wide incident beam gradually becomes a SLOC beam (with constant width). The parameters are , for the incident beam and .
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