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In the opposite limit σ ≥ σ $^{∗}$, the amplitude of electromagnetic waves becomes large but the oscillations of Bessel functions are strongly suppressed. Therefore, the amplitude of I (1) F is still small. The averaged value of I (1) F can be also expressed through a single parameter σ 

as 

<img src='content_image/330614.jpg'>

In this limit, the amplitude of Fiske resonance weakly depends on the density of Abrikosov vortices, displaying a small maximum on σ ≃ σ $^{∗}$. Notice here, that this regime can be easily realized for low-dissipative junctions as γ << ω$_{0}$ . 

## V. JOSEPHSON JUNCTIONS WITH MISALIGNED ABRIKOSOV VORTICES: EXPERIMENTAL SETUP AND MEASUREMENTS 

The experiments were carried out on the Nb − AlO$_{x}$ − Nb Josephson tunnel junction of square geometry and dimensions of 50 × 50 µm $^{2}$. Details of the fabrication process are reported in [29, 30]. 

The junction was mounted on the sample holder inside a closed copper box in order to prevent the influence of the electromagnetic noise. The box was immersed in a liquid helium bath, so all measurements were done at a stable temperature T = 4 . 2 K . In order to heat the junction above the superconducting transition temperature T$_{c}$ , a SMD 100 Ohm resistor was used as a heater mounted in contact with the sample holder. A special coil system containing two Helmholtz copper coils was used in order to generate both the magnetic fields perpendicular to the junction plane B$_{⊥}$ and the magnetic field parallel to the junction plane B$_{‖}$ . The shielding of the sample from the Earth magnetic field and from the electromagnetic noise was reached by using a three level µ -metal shielding system and a one level Al -shield. The accurate measurements both the Josephson critical current I$_{c}$ , and the amplitude of the first Fiske step I (1) F were achieved by a careful shielding and by inserting cold low pass filter, mounted just near the sample. First, we measured the I − V curves of the junction without trapped Abrikosov vortices. We tuned the amplitudes of Fiske resonances by an externally applied magnetic field B$_{‖}$ . Fig.2 shows the typical I − V curves where the amplitude of the first Fiske step was maximized (open circles) and suppressed (closed circles). The first I − V curve was used in order to obtain the voltage position of the Fiske step V$_{1}$ ,, while the second one was utilized for experimental estimation of the quasiparticle 

