# Does absorption in the cladding material change the real value of the propagation constant of a waveguide?

Imagine two scenarios: two cladding materials with the same real refractive index, but one has absorption while the other does not. Now, these materials act as the top cladding of a waveguide (for simplicity, let's assume there is no absorption in the core material).

Is the real part of the propagation constant of the waveguide, beta, the same for both scenarios? Or does the presence of absorption change the real value of the propagation constant of the waveguide?