Nonlinearity and wideband parametric amplification in an NbTiN microstrip transmission line

The nonlinear response associated with the current dependence of the superconducting kineticinductance was studied in capacitively shunted NbTiN microstrip transmission lines. It was foundthat the inductance per unit length of one microstrip line could be changed by up to 20% byapplying a DC current, corresponding to a single pass time delay of 0.7 ns. To investigate nonlineardissipation, Bragg reectors were placed on either end of a section of this type of transmissionline, creating resonances over a range of frequencies. From the change in the resonance linewidthand amplitude with DC current, the ratio of the reactive to the dissipative response of the linewas found to be 788. The low dissipation makes these transmission lines suitable for a number ofapplications that are microwave and millimeter-wave band analogues of nonlinear optical processes.As an example, by applying a millimeter-wave pump tone, very wide band parametric amplicationwas observed between about 3 and 34 GHz. Use as a current variable delay line for an on-chipmillimeter-wave Fourier transform spectrometer is also considered.