High-Efficiency Ka-Band Frequency Multiplier Based on the Non-Linear Kinetic Inductance in a Superconducting Microstrip

LO sources have become a major technological deficit approaching the THz frequencies. Forapplications where a narrow linewidth is necessary, such as coherent remote sensing, the best solutionto signal generation is frequency multiplication, where phase locking can be easily achieved usingthe fundamental source. We present an alternative to existing frequency multiplier technologiesfor cryogenic applications. The device is a superconducting waveguide that has kinetic inductancedependent on the rf current through the device. The non-linear kinetic inductance is anomalousto a non-linear optical medium where the Kerr effect causes 3- or 4-Wave mixing, as demonstratedin microwave parametric amplifiers utilizing the same non-linear effect. In 4-Wave mixing, threephotons at the fundamental frequency mix to generate a single photon at the third harmonic.Dispersion engineering is used to achieve wide-band phase matching and phase out harmonics higherthan the third .The device length is designed to be the point where most photons are up-convertedto the third harmonic. Simulations of these devices lead to expected efficiencies as high as 90%. Wereport the first results from a NbTiN frequency multiplier from 34.2 GHz to 104 GHz with efficiencyapproaching 60%.