Design and preliminary test of a kinetic inductance millimeter-wave converter

Recent theoretical work suggests the millimeter-wave band as an attractive mass range for axion dark matter experiments. Extending current axion searches to this substantially higher regime will therefore require frequency tunable, millimeter-wave receivers. Moreover, the exceedingly low power converted by an axion signal constrains these devices to operate at the quantum limit or below it. Here we discuss a device which exploits the nonlinear kinetic inductance of thin-film NbTiN to perform parametric interactions between spatially and spectrally disparate, low-loss modes. The device consists of a millimeter-wave input parametrically coupled to a microwave output by a flux-tunable ring modulator element. We delineate the constraints posed by the axion search apparatus, detail the design parameters, and, finally, present preliminary results demonstrating the device's nonlinearity and frequency tunability.