[en] The order parameter response function of a superconductor can be obtained by incorporating it in an asymmetric tunneling junction with a higher T/sub c/ superconductor and measuring an excess current in the I-V characteristic. This current is then proportional to the imaginary part of the space and time Fourier transform of the response function with the frequency set by the bias voltage and the wave vector determined by a magnetic field applied parallel to the plane of the junction. Using this technique, studies of the dynamics of the superconducting order parameter have been undertaken above and below T/sub c/. Above T/sub c/ the time dependent Ginzburg-Landau equation accurately describes the dynamics. Below T/sub c/ a propagating mode is found which can be associated with fluctuations in the phase of the order parameter. Measurements of the magnetic impurity dependence of the response function have been used to study the ''anomalous'' term in the Gor'kov-Eliashberg theory which gives the coupling between order parameter fluctuations and fluctuations in the quasiparticle distribution function. Below T/sub c/ and in a current-carrying state, amplitude and phase fluctuations are coupled and the modes soften at the critical current