Complex Coupling Coefficient - what is the length dimension and difference from a coupling constant?
Dear forum and fellow Lumerical users,
We are trying to simulate the coupling coefficient between two neighbouring waveguides to predict the behaviour in a waveguide arrray and follow the usual commands from Lumerical that give either the 'complex coupling coefficient' or the 'power coupling' as below:
out = overlap("test_mode1","test_mode2"); ?out(1); # overlap ?out(2); # power coupling ?coupling("test_mode1","test_mode2"); # the complex coupling coefficient ?abs(coupling("test_mode1","test_mode2"))^2; # same as out(2), the power coupling
However, there has been ample confusion about its similarity to the coupling constant kappa, the ordinary 'coupling coefficient' and especially the dimensions.
My questions are therefore :
1. Are the coupling coefficients formulated as per /um or /mm ?
2. Does the complex part refer to losses?
3. Is this the same as the 'coupling constant' or 'coupling coefficient' that waveguide papers commonly refer to?
I would be sincerely grateful for a clarification and thank you very much in advance!