Advances in Superconducting Nanowire Detectors: Single Photon Array Development and Linear Kinetic Inductance Response

The work covered in this dissertation addresses two areas revolving around superconducting nanowire detector development. The first is regarding array architectureused for a large-scale system. The second involves operating under conditions that allow for a linear response in a superconducting nanowire detector. This dissertation provides the relevant theory, design, and measurements to characterize these detectors. The array architecture studied here utilizes a superconducting nanowire single photon detector embedded in an LC resonant structure, allowing multiple pixels to couple to a single transmission line and identify each one by a tuned characteristic frequency. The pixels in the array are DC-biased, allowing them to respond to absorbed single photons and avoiding any dead time associated with RF biasing. Measured results from a 16-pixel array based on chip components are analyzed. The development here directs this architecture towards integrating a proven 16-pixel design onto a single substrate with the capacity to scale to a higher pixel count and integrate into a broad range of applications. This text outlines the theory behind the proposed linear operation regime and details the considerations needed to achieve a response. The basic principle relies on the time-dependent change in kinetic inductance due to an absorbed photon. Under the conditions discussed in the text, this would allow for fast photon number resolution. However, without reaching those conditions, the detector may still operate under a higher incident photon flux. Two device designs are formulated and simulated, weighing the benefits and drawbacks of each approach. One of the device designs uses an impedance-matching taper to minimize reflections between the nanowire and 50 Ohm amplifier. The other design utilizes N parallel nanowires spanning the length of a gap along a 50 Ohm transmission line path. The tapered device is realized to a proof-of-principle stage and measured under conditions that set a limit on the device’s linear response to optical power. The performance of this detector points to areas of improvement that are addressed or circumvented in the parallel bridge design. Potential for future development is discussed for the frequency multiplexed superconducting nanowire single photon detector array and the linear mode detector.