Grating-coupler assisted infrared spectroscopy on anisotropic multilayer systems: A comparative study

We examine two different methods to calculate the electromagnetic fields and the optical properties of multilayer structures of anisotropic media with gratings: (i) A modal-expansion method and (ii) a coupled-wave method. We show that both methods, which have been developed independently for different fields of applications and implemented on different platforms, give the same results to a very high precision. This is true even for such very crucial cases like for the higher-order excitation maxima of the (0-0) intrasubband plasmon ω00p or of the lineshape concerning any details in the spectrum of the (1-0) intersubband plasmon ω10p of a quasi-two-dimensional electron gas of GaAs-Ga1−xAlxAs multilayer structures with a finite height silver grating on top of the sample.