UC Santa Barbara

High contrast imaging is a powerful technique for studying exoplanets and circumstellar disks. Ground based observations rely on adaptive optics to correct wavefront aberrations and starlight suppression techniques such as coronagraphy to reach contrast levels suitable for detecting substellar companions. Sensitivity is limited by coherent interference patterns, called speckles, in the science focal plane resulting from imperfect wavefront correction. As adaptive optics systems and methods for mitigating speckles from non-common path errors have matured in recent years, the contrast ratios remain limited by atmospheric speckles with lifetimes $<$ 1 sec.

Microwave kinetic inductance detectors (MKIDs) are fast photon counting detectors that can simultaneously measure a photon's arrival time, its energy, and its x-y location within the focal plane. Armed with these capabilities, MKID science cameras promise to substantially improve the signal to noise of exoplanet and circumstellar disk detections by sampling speckle intensities quickly with photon limited noise.

In this thesis I present the development of an MKID-based science camera for a NASA funded balloon-borne observatory called PICTURE-C (the Planetary Imaging Concept Testbed Using a Recoverable Experiment-Coronagraph). The balloon will fly at an altitude of $\approx$ 40 km, placing it above most of the atmosphere and thereby removing atmospheric aberrations, with the goals of characterizing nearby debris disks and demonstrating the operation of MKIDs in a near space environment.

I will then discuss photon counting stochastic speckle discrimination, an analysis technique in which the variability of inter-photon arrival times is used to separate residual stellar speckles from companion light. This technique can improve the signal to noise of planet detections over that of long exposures where many speckle realizations are averaged over.

Finally I present a tunable coupler that can be used to adjust the effective coupling strength between a superconducting microresonator and its microwave feedline in situ for low temperature measurements. This scheme may find applications in astronomy for optimizing the readout of MKIDs or in quantum information science for optimizing qubit lifetimes.