Abstract
The nonlinear response associated with the current dependence of the superconducting kinetic inductance was studied in capacitively shunted NbTiN microstrip transmission lines. It was found that the inductance per unit length of one microstrip line could be changed by up to 20% by applying a DC current, corresponding to a single pass time delay of 0.7 ns. To investigate nonlinear dissipation, Bragg reflectors were placed on either end of a section of this type of transmission line, creating resonances over a range of frequencies. From the change in the resonance linewidth and amplitude with DC current, the ratio of the reactive to the dissipative response of the line was found to be 788. The low dissipation makes these transmission lines suitable for a number of applications 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 amplification was observed between about 3 and 34 GHz. Use as a current variable delay line for an on-chip millimeter-wave Fourier transform spectrometer is also considered.
Highlights
The nonlinearity of superconducting kinetic inductance has been explored for a number of device applications including kinetic inductance traveling-wave parametric amplifiers (KITWPAs) [1], current sensors [2], magnetometers [3], variable inductors [4], delay lines [5], and even qubits [6]
We have explored the nonlinear kinetic inductance and dissipation of NbTiN microstrip transmission line structures that use a series of microstrip stubs to achieve a 50- characteristic impedance
At 8.4 GHz, the device loss of 0.35 dB has been measured through a 93-mm length of the microstrip line, corresponding to 333 wavelengths, using an on-chip Fabry-Pérot interferometer
Summary
The nonlinearity of superconducting kinetic inductance has been explored for a number of device applications including kinetic inductance traveling-wave parametric amplifiers (KITWPAs) [1], current sensors [2], magnetometers [3], variable inductors [4], delay lines [5], and even qubits [6]. These nonlinear kinetic inductance devices differ in a number of ways from corresponding devices based on the nonlinear inductance of Josephson junctions. We characterize the loss and nonlinearity in sections of this transmission line and demonstrate its use as the basis for a variable delay line for an on-chip Fourier transform spectrometer and as a very-wide-band parametric amplifier
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