Nonlinear HTS lumped elements in microwave transmission and resonance circuits

The present work is devoted to investigation of nonlinear lumped element (NLE) in form of short (l<;λ) and narrow (w=3.5-10 μm) constriction within a HTS microstrip line. HTS microstrip lines used in our studies were produced from thin (200nm) YBCO films, obtained by pulse laser deposition (PLD) on singlecrystal CeO₂-buffered sapphire substrates. The NLE were produced by use of standard photolithography technique and were positioned in YBCO microstrip transmission lines or in the central part YBCO microstrip resonators for farther microwave experiments by use of resonant and nonresonant methods. Calculations have shown that this type of NLE, because of its smallness, can be considered as a resistive element and its reactive response can be disregarded. The current density within this type of NLE reaches the values close to the critical current density at input power values Pin<;10mW, because of small NLE width w comparatively to the basic line width W(W/w=140).