Figure 1

The IV characteristics of a stack with 10 coupled JJs without irradiation (curve 1) and under radiation with frequency $\omega =2$ and amplitude $A=0.1$ (curve 2) and amplitude $A=0.5$ (curve 3). The filled arrows indicate the positions of the fundamental parametric resonance (fPR), while the hollow arrow indicates the radiation related parametric resonance (rrPR).Reuse & Permissions

Figure 2

(a) The illustration of the modulation of the charge oscillations in the fundamental parametric resonance region ($I=0.2792$) at $A=0.1$. $L1$ and $L2$ show charges in the first and second superconducting layers, respectively. (b) $Q\left(t\right)$ dependence together with the IV characteristics (black curve with the symbols related to the right and upper axes) in the radiation related parametric resonance region at $A=0.5$. The ellipse part of the IV characteristics shows the “bump” structure. The arrow indicates the position of the Shapiro step (SS) in the IV characteristics as well.Reuse & Permissions

Figure 3

Demonstration of the change in the wavelength of the longitudinal plasma mode at the fundamental parametric resonance with increase of the amplitude of radiation. The numbers count the layers in the stack. (a) $A=0$, before resonance. (b) $A=0$, at resonance. (c) $A=0.15$. (d) $A=0.23$. (e) The longitudinal plasma wavelength at the fundamental parametric resonance (fPR) (filled squares) and radiation related parametric resonance (rrPR) (empty circles) in the amplitude interval $(0,0.35)$ at $\omega =2$.Reuse & Permissions

Figure 4

(a) IV characteristics of a stack with 10 coupled JJs under radiation with amplitude $A=0.005$ and different frequencies. The thick curve (black online) shows IV characteristics without irradiation. Inset: Coincidence of the curves before the Shapiro step. (b) Demonstration of the Shapiro step “charging.” We show the IV characteristic with the Shapiro step (CVC, right and upper axes) together with a time dependence of the charge in the superconducting layer. Inset 1: Enlargement of the charge oscillations in the parametric resonance region. Insets 2 and 3: Enlargements in consecutive order of the charge oscillations in the Shapiro step region.Reuse & Permissions

Figure 5

(a) IV characteristics of a stack with 10 JJs at $\omega =1.151$ and different amplitudes of radiation. Inset 1: Enlargement of the part with small $A$. Inset 2: Charge-time dependence at $A=0.06$ together with IV characteristic (dark curve with the symbols with right axis for the voltage and upper axis for the current). (b) Demonstration of Shapiro step width changing for single JJ (filled squares) and stack of intrinsic JJ (empty squares) at $\omega =1.151$. (c) The same at $\omega =2$.Reuse & Permissions