Dispersion of a double metal waveguide of a quantum cascade laser in the optical phonon region of GaAs

Analytical calculations of the dispersion characteristics of the guided modes in a double metal (DM) waveguide of a quantum cascade laser (QCL) in the optical phonon region in GaAs based on the modified Marcatili method are presented. The calculation results correlate well with the results of the numerical solution of the Helmholtz equation at optical phonon frequencies of GaAs. It is shown that the dominant mode E$_{00}^y$ far from the phonon resonance of GaAs ceases to be such for frequencies near this resonance, what makes E$_{10}^y$ mode the dominant mode at these frequencies.