Utilizing Nonlinearity in a Superconducting NbN Stripline Resonator for Radiation Detection

We study a microwave superconducting stripline resonator made of NbN on a sapphire substrate. A radiation detector (RD) having a thin meander shape is integrated into the resonator. We harness an extremely strong nonlinear instability occurring in the device in order to enhance its sensitivity to infrared radiation impinging on the RD. Characterization measurements yield a noise equivalent power of 34 fW/radicHz at a modulation frequency of 7.74 GHz. Such a device may be exploited for fast and sensitive radiation detection.