HgCdTe APD Arrays for Astronomy: Natural Guide Star Wavefront Sensing and Space Astronomy

This dissertation describes work I have conducted over five academic years 2013/14 through 2017/18 as a NASA Space Technology Research Fellow at the University of Hawai'i Institute for Astronomy. The focus has been the characterization and improvement of the Selex Avalanche Photodiode HgCdTe InfraRed Array (SAPHIRA), a 320 × [email protected]μm pitch metal organic vapor phase epitaxy mercury cadmium telluride array that provides new capabilities and performance for near infrared (NIR) astronomy. This has involved more than a dozen arrays, working closely with the manufacturer so as to provide feedback for improvement of the next generation.

The investigation has resulted in three lead authored publications in the Astronomical Journal which, as published, constitute the core of this dissertation: 1. An investigation into the SAPHIRA's dark current, a critical performance characteristic of astronomical detectors that determines the inherent background of observations. This dark current is comparable to other NIR devices. Published as Atkinson et al. (2017b). 2. The SAPHIRA's ability to detect individual photons, an ability referred to as photon counting. Counting NIR photons gives unique new capabilities in AO and for future time-resolved scientific applications. The SAPHIRA is the only device of this size with these capabilities. Published as Atkinson et al. (2018). 3. The characterization of Kepler Objects of Interest and contaminating companions performed with Near Infrared Camera 2 (NIRC2) on the Keck II telescope, following on their discovery by the Palomar 1.5-m (P1.5-m) telescope's Robotic-Adaptive Optics (Robo-AO) instrument. Published as Atkinson et al. (2017a).

These are preceded by chapters providing 1) an introduction, 2) a description of the SAPHIRA array, 3) a more detailed treatment of setup and characterization together with 4) a chapter covering telescope deployments. They are followed by a chapter covering the three NASA Site Experiences performed as part of my Space Technology Research Fellowship. The dissertation concludes with a brief summary of my most significant achievements.