FIG. 2: (Color online) The dispersion curve (Ω = ω/ω$_{J}$ versus κ = cq/ω$_{J}$ ε 1 / 2 $_{ext}$) for SJPWs at the vacuum-layered superconductor interface. The values of the parameters are: γ = 200 , ε = 16. Inset: zoom-in of the spectrum near the point ( κ = 1 , Ω = 1). Points A and B correspond to the beginning and end of the high-frequency branch. The green dashed line is the vacuum light line Ω = κ . insulator increases, the point A in Fig. 2 moves towards point B, and the gap in the SJPW spectrum increases. When ε$_{ext}$ = ε (1 − 1 /γ $^{2}$) ≈ ε , the points A and B coincide, and the high-frequency branch in the SJPWs spectrum disappears. Note that the Josephson current is small with respect to the displacement current at high frequencies, Ω ≫ 1. In this case, we can omit 1 in the denominator in Eq. (7). This corresponds to the dispersion relation for a periodic layered structure without coupling between superconducting layers . Specifically, the interlayer Josephson coupling is responsible for the appearance of a frequency gap, ω$_{J}$ < ω < ω$_{1}$ , in the spectrum of SJPWs. Excitation of the SJPWs above ω$_{1}$ .— It is known that the excitation of surface waves is accompanied by the so-called Wood anomalies of the reflectivity and transmissivity coeffi- 7