TM and TE optical modes of the planar anisotropic aluminum-doped zinc oxide waveguides at the epsilon-near-zero spectral point

In this work, we investigate the guided mode properties of planar anisotropic aluminum-doped zinc oxide waveguides (air/metamaterial/silicon oxide) at the epsilon-near-zero spectral point. Our calculations predict two fundamentally different propagation regimes for the lowest order guided TM and TE modes over a broad spectral range (400-2000 nm). Our study shows that excitation of the TM guided mode is possible for wavelengths higher than epsilon-near-zero spectral point. However the propagation distance for such a TM mode will strongly depend on the spectral position of the mode’s eigenfrequency. E.g., propagation distance is maximized for eigenfrequencies near epsilon-near-zero point and reduced by an order of magnitude as the eigenfrequency is tuned by ~50 nm.