Harmonic frequency mixing in Bi2Sr2CaCu2O8+X intrinsic Josephson junctions

In a c-axis junction stack (10 mu mx10 mu m in a-b plane) patterned on a Bi 2Sr2CaCu2O8+X single crystal, we performed harmonic mixings between a 100 G Hz signal and up to the 98th harmonic of a local oscillator at about 1 GHz. The dependence of P-IF on V, where P-IF is the mixing output at the interm ediate frequency and V is the dc voltage across the junction stack, was str ongly affected by the local oscillator power levels. For low values of loca l oscillator power, the optimum operation point where P-IF became maximum w as around zero bias, and typical multi-branch structure of P-IF vs V curves were observed. For high values of local oscillator power, the optimum oper ation point moved to the high-voltage region. In both cases, interesting os cillations occurred on the P-IF vs V curves. Our experimental results led u s to believe that intrinsic Josephson junctions can be good candidates for high frequency applications and the harmonic mixing may be a useful probe t o investigate plasma phenomena in the layered superconductors. (C) 1999 Ame rican Institute of Physics. [S0003-6951(99)05341-3].