If the bulk coupling material is not highly absorbing (i.e. light may return to the front/back surface multiple times before being absorbed), but has k > 0, the angular direction in which light travels is ambiguous. Theta has to be complex for the plane-wave approximation to be valid, but it is possible to calculate the (real) angle from which power is incident. Calculating the 'power angle' is not currently implemented.
If the bulk coupling material is not highly absorbing (i.e. light may return to the front/back surface multiple times before being absorbed), but has k > 0, the angular direction in which light travels is ambiguous. Theta has to be complex for the plane-wave approximation to be valid, but it is possible to calculate the (real) angle from which power is incident. Calculating the 'power angle' is not currently implemented.