The Initial Values node adds initial values for the electric field envelopes for the first and second waves, which can serve as an initial guess for a nonlinear solver. Add more 
Initial Values nodes from the 
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    Enter values or expressions for the initial values of the components of the Electric field envelope, first wave E1 and 
Electric field envelope, second wave E2 (SI unit: V/m). The default values are 0 V/m. The second wave is applicable if the Wave Vectors are bidirectional.