define "Propagation constant" in the case of Grating

Hello dear friends
I have a trouble to define "Propagation constant" in the case of Grating..!
How should "Propagation constant" be defined in port1,2 (Electromagnetic Waves, Frequency Domain) at COMSOL multiphysics? the file is attached
Please help me 😣raja_poster.pdf

It depends on the wavelength.

The so-called propagation constant, the imaginary part of which quantifies the phase delay per unit propagation distance.

Since the propagation constant is a complex quantity we can write:

γ = α +i β = √(Series admittance/Shunt reactance)

where

α, the real part, is called the attenuation constant
β, the imaginary part, is called the phase constant

for ideal conductors, β=ω√(LC)

Hello dear SunnySkyguy

Do you study paper of "Surface Plasmon Resonance Sensors: Optimization of Diffraction Grating and Prism Couplers" ?


How should β (Propagation constant) be defined in port 1 and 2?



Dear SunnySkyguy, Please explain details.. I'm very confused!

I have trouble to define "Propagation constant" in the case of Grating..!

Thank you so much