@Preben Alsholm

Hi,

First of all, thanks for the help. It's been some time since I've used Maple so there may be some mistakes such as the ones you mentioned. 

I've seen that you're right with the implicitplot, but it still doesn't plot anything at all even though the range is quite the correct one. I'll try and solve it some other way.

btw, if you wanna know, kzp and kzm are the positive (plus) and negative (minus) wavenumbers in z direction (kz+ & kz-).