Resonant and Conversion Reflections of Electromagnetic Waves from a Crystal-Metal Interface

The exact dispersion equations describing the resonant excitation of a polariton-plasmon at the crystal-metal interface, which were previously analytically studied within the approximate impedance approach, have been numerically analyzed. The results of an exact numerical analysis and an approximate analytical consideration almost coincide in the long-wave limit (IR region). Conversion arises simultaneously with the resonance: the incident pump wave is completely converted into a polariton of the other polarization branch, which is localized at the crystal boundary, while the amplitude of the reflected bulk wave of the same branch is zero. When passing from the IR range to the visible region, the decrease in the wavelength leads to an increasing difference in the conditions for the existence of resonance and conversion reflections and the height of the resonance peak becomes distinctly smaller than the value predicted by the approximate theory. The parameters of the resonant and conversion reflections have been calculated for optically uniaxial saltpe- ter and calomel crystals with an aluminum coating for the wavelength range of 0.4–5.0 μm.