Improving the Resolving Power of Ultraviolet to Near-Infrared Microwave Kinetic Inductance Detectors

Abstract

dark matter searches to biological imaging and astronomy. The performance of these de tectors often limits the achievable science goals for an application, so improvements to detector technologies can be transformative. This dissertation focuses on these detector enhancements, emphasizing the requirements for one particular application, exoplanet di rect imaging. However, the work done here remains broadly applicable to fields needing highly sensitive sensors in this wavelength range.Finding and studying the properties of exoplanets orbiting distant stars can tell us much about solar system dynamics and the formation of our own solar system. With sufficiently precise measurements we might also discover the presence of water or even biological processes on these planets. To achieve this goal, we need astronomical instrumentation ca pable of separating an exoplanet's light from its host star by directly imaging it. For many exoplanets, though, we receive at our telescope only roughly one photon for every billion from the star. Even worse, these two light sources often partially overlap because of the relative closeness of exoplanets to their stars and the diffraction limit set by the finite size xi of our telescope optics. Therefore, the extreme contrast ratio between the brightness of the star and planet sets the performance requirements for this kind of instrument.Carrying out this measurement with the traditional semiconductor based sensors can be difficult. They detect the intensity of light at each pixel and introduce excess noise into the system. However, superconducting sensors avoid this limitation because of their ex tra sensitivity. Each individual incident photon can be resolved making them essentially perfect photon counting detectors, which enables the detection of exoplanets with more challenging contrast ratios than detectable with conventional detectors. The system noise in a superconducting sensor, instead, determines how accurately the photon energy can be measured through the size of the detector response. Because of this extra energy measure ment capability these detectors do not need the complicated optical systems typically used to measure an exoplanet's atmospheric spectrum. The accuracy at which we can resolve these planetary spectra determines how much we can learn about a planet and, as such, is the principal metric for the performance of these devices.The Microwave Kinetic Inductance Detector (MKID) is unique among other supercon ducting technologies because it allows for the simple readout of tens to hundreds of thou sands of pixels, which is a requirement for when the exact location of an exoplanet is un known. This dissertation focuses on improving the spectral resolving power of MKIDs to make them the superior option for ultraviolet to nearinfrared measurements and, in partic ular, for exoplanet direct imaging. Chapters 1 and 2 discuss the significance of MKIDs as astronomical detectors and the relevant physics needed to understand their operation. In the following chapters, four sepa...

A High-Sensitivity Cryogenic Radio Receiver: Design, Performance and Polarization Analysis

“…For discrete radio sources, especially in telecommunication, a common figure of merit to measure the antenna sensitivity is G/T sys ratio where G is the gain of the antenna and T sys is the system temperature 7 . Reducing the physical temperature of the receiver using a cryogenic system effectively lowers the system's noise, which contributes to achieving a higher sensitivity [8][9][10] . For example, the Atacama Large Millimeter/submillimeter Array (ALMA) 11 , and Green Bank Telescope (GBT) 12 are wellknown radio telescopes that utilize the cryogenic system to lower the T sys .…”