$RCWArefractiveindex

The $RCWArefractiveindex command is used to define the refractive index in each region with different wavelength.

$RCWArefractiveindex

[n_{1,1} n_{1,2} n_{1,3}]-lambda1  [n_{1,1} n_{1,2} n_{1,3}]-lambda2                layer1 - Nlambda * xdiv 
[n_{2,1} n_{2,2} n_{2,3}]-lambda1  [n_{2,1} n_{2,2} n_{2,3}]-lambda2                layer2 - Nlambda * xdiv 
...
total layer

The $RCWArefractiveindex setting in GUI interface is here
1. Press Add new layers for RCWA and fill in the fields as needed!