content_image/333801.jpg
<img src='content_image/333801.jpg'>

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- 

