Copyright by Michael Anthony Gully-Santiago 2015 The Dissertation Committee for Michael Anthony Gully-Santiago certifies that this is the approved version of the following dissertation: Innovative Technologies for and Observational Studies of Star and Planet Formation Committee: Daniel Jaffe, Supervisor John Lacy Neal Evans Adam Kraus Alycia Weinberger Innovative Technologies for and Observational Studies of Star and Planet Formation by Michael Anthony Gully-Santiago, B.A. ASTRO. & PHYS. DISSERTATION Presented to the Faculty of the Graduate School of The University of Texas at Austin in Partial Fulfillment of the Requirements for the Degree of DOCTOR OF PHILOSOPHY THE UNIVERSITY OF TEXAS AT AUSTIN May 2015 Dedicated to all my teachers. Acknowledgments This work would not have been possible without the mentorship of my collaborators Katelyn Allers and Alycia Weinberger, for which I am deeply indebted. I acknowledge the mentorship and patience of my former student colleagues Dr. Jasmina Marsh and Dr. Casey Deen. I am grateful for the efforts of my junior colleagues Jared Rand, Amanda Turbyfill, and Carleen Boyer for their contributions to the Silicon Diffractive Optics Group. Engineers Weisong Wang and Cindy Brooks contributed substantially to the Si diffractive optics fabrication. I am indebted to my NASA GRSP mentor Daniel Wilson, with whom it was a pleasure to work. I am thankful for the supervision of Richard Muller and Victor White at the Microdevices Laboratory. Sungho Lee, Hyeonju Jeong, Taylor Chonis, Mike Pavel, Michelle Grigas, Neal Evans, John Lacy, and Adam Kraus, Rachel Walker, and Gordon Orris made this work possible. I am delighted to acknowledge support from the NASA Graduate Stu- dent Research Program (GSRP) Fellowship, grant NNX10AK82H. Portions of this research were supported by NASA APRA grant NNX10AC68G, NASA ACT grant NNX12AC31G, NSF ATI grant AST-0705064, and NASA Origins grant number NNX07AI83G. MGS acknowledges support from the Univer- sity of Texas in the form of the Graduate Dean's Prestigious Fellowship and v from the Department of Astronomy in the form of the David Benfield Memo- rial Fellowship in Astronomy. Funding from the McDonald Observatory and the Department of Astronomy's Cox graduate student excellence funds have helped to support travel and other aspects of this research. Part of the re- search was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Ad- ministration. Some of the work was carried out at the University of Texas under a contract from the University of Arizona. The development work for the grisms was supported in part by NASA (grant number NNX07AV15H). The authors wish to thank Gary Poczulp and the National Optical Astronomy Observatory for assistance in producing some interferograms of early grating prototypes. Thank you to David Hogg, Dan Foreman-Mackey, Jonathan Sick, Jake Vanderplas, and the participants and organizers of the Astro Data Hack Week (2014). This dissertation includes data gathered with the 6.5 meter Magellan Telescopes located at Las Campanas Observatory, Chile. I was lucky to be part of such a talented and creative group of incoming graduate students- Chris, John, Chalence, JJ, Julie, Manuel, Erik, Paul, and Manos. I look forward to following their promising careers, and crossing paths indefinitely. Joi Ito and Datri Bean enhanced my creativity. Thank you to my supportive family members Diana, Tony, Erika, and Vanessa who gave me mettle. Thank you to Carol for bringing Chelsey into the world, to Alese for introducing us, and to Chelsey for being exceptionally supportive. Thanks to Mr. Emerson who got me started in astronomy. Thanks to all my friends. vi I acknowledge the kindness of the Wolchover family, who have always been outstanding in their field. A very special thank you is reserved for my advisor, Daniel Jaffe, for contributing so deeply to my professional growth. In particular I acknowledge his patient editing of the prose in this document. vii Innovative Technologies for and Observational Studies of Star and Planet Formation Publication No. Michael Anthony Gully-Santiago, Ph.D. The University of Texas at Austin, 2015 Supervisor: Daniel Jaffe I summarize the optical design, fabrication, and performance of sili- con diffractive optics for astronomical spectrographs. The first set of optical devices includes diffraction-limited, high-throughput silicon grisms for JWST- NIRCam. These grisms served as pathfinders to Silicon immersion gratings, which offer size and cost savings for high-resolution near-infrared spectro- graphs. I demonstrate the production and optical evaluation of the immersion grating that enabled IGRINS at the McDonald Observatory. This grating pro- vides spectral resolution R = 40; 000 over the H− and K− near-infrared band atmospheric windows (1.5−2.5 µm). Electron-beam lithography offers much higher precision over contact mask photolithography for the production of Si immersion gratings. Electron-beam patterned prototypes are stepping-stones to monolithic Si gratings for iSHELL and GMTNIRS. The monolithic design viii of Si immersion gratings presents a limitation for scaling up the grating size, since existing fabrication equipment cannot handle monolithic silicon pucks. The size limitation can be overcome by direct-bonding Si substrates to op- tical prisms. I demonstrate a technique to measure interfacial gaps as small as 14 nm between the bonding interfaces, which produce 0.2% transmission loss. These technologies will enable the direct measurement of the atmospheric properties of extrasolar planets in the next decade. IGRINS is now measuring fundamental properties of young T-Tauri stars; low mass young brown dwarfs are below the sensitivity limit of existing high spectral resolution near-IR spec- trographs. My approach to the discovery and characterization of young brown dwarfs therefore employs low resolution (R ∼ 2000) near-IR spectroscopy. I confirm and characterize 17 candidate young stars and brown dwarfs reported by Allers and collaborators. All 17 sources have circumstellar disks. Using deep optical, near-infrared, and mid-infrared photometry, I search an off-core region towards the nearby ∼ 1 Myr Ophiuchus star forming clus- ter for candidate young stars and brown dwarfs. Multi-object I−band spec- troscopy of 419 candidates reveals 12 new members. Ten of these have no evidence for mid-IR excess emission from 3.6 to 8.0 µm. The disk fraction for spectral types M4 and later towards this region of Ophiuchus is 5/15. Two of the disk sources have edge-on disks, pointing to a high edge-on disk fraction. I discuss possible sources of contamination in the survey. ix Table of Contents Acknowledgments v Abstract viii List of Tables xv List of Figures xvii Chapter 1. Introduction 1 1.1 Innovative Technologies for Star and Planet Formation . .1 1.2 Observational Studies of Star and Planet Formation . .8 1.3 Summary . 15 Chapter 2. High Performance Silicon Grisms for 1.2-8.0 µm: Detailed Results from the JWST-NIRCam Devices 16 2.1 Introduction . 16 2.2 Discussion of Loss Mechanisms . 18 2.2.1 Surface Flatness . 18 2.2.2 Groove Geometry . 20 2.2.3 Microscopic Surface Roughness . 21 2.2.4 Fresnel Losses . 21 2.3 Results of Anti-Reflection Coating . 22 2.4 Conclusions . 28 Chapter 3. Near infrared metrology of high performance silicon immersion gratings 30 3.1 Introduction . 30 3.2 Overview . 31 3.3 Efficiency . 34 x 3.4 Refractive index dependence . 38 3.5 Periodic errors, ghosts, and large scale performance . 41 3.6 Measurement setup description . 44 Chapter 4. High Performance Si Immersion Gratings Patterned with Electron Beam Lithography 46 4.1 INTRODUCTION . 46 4.2 On-sky performance of Si immersion grating . 48 4.3 Motivations for direct writing Si immersion gratings . 49 4.3.1 Motivation #1: Higher precision than contact lithog- raphy . 50 4.3.2 Motivation #2: Finer groove pitch capability . 51 4.4 e-beam patterning strategies . 51 4.4.1 e-beam patterning scale size hierarchy . 52 4.4.1.1 e-beam step size and spot size . 54 4.4.1.2 Subfield deflector . 55 4.4.1.3 Field deflector . 56 4.4.1.4 Interplay of hierarchy at boundaries and de- sign rules . 56 4.4.2 Predicting the ghost level associated with field posi- tioning errors . 59 4.4.3 Employ multiple field sizes rather than one field size 61 4.4.4 Strategies for mitigating facet position errors attributable to large scale stage drift . 63 4.4.5 Characterization of e-beam stage drift . 63 4.5 Results: Test gratings produced with e-beam patterning . 65 4.5.1 Measurement of ghost levels for a variety of writing strategies . 65 4.5.2 Improvement in wavefront performance from drift cor- rection . 67 4.6 Limitations of direct writing Si immersion gratings . 67 4.6.1 Serial write process yields long write times . 67 4.6.2 Large per-part investment cost yields heightened pro- cess risk . 70 4.6.3 Experiments with negative resist . 70 4.7 Conclusions . 71 xi Chapter 5. Optical characterization of gaps in directly bonded Si compound optics using infrared spectroscopy 73 5.1 Introduction . 73 5.2 Si−Si Fabry P`erotmeasurement theory . 78 5.2.1 The Si−Si interface gap is a low finesse Fabry-P`erot etalon . 78 5.2.2 Predicted transmission spectrum for bonded Si with finite interface gap . 82 5.3 Laboratory demonstration: Embedding gaps of known sizes . 85 5.3.1 IR bubble imaging and limitations . 89 5.4 Measurement technique and correlated measurement errors . 90 5.5 Results of infrared spectroscopy of directly bonded Si . 92 5.5.1 Spectra of direct bonded Si with known gap sizes . 95 5.5.2 Spatially resolved measurements with Sample Trans- port Accessory . 96 5.5.3 What is the smallest gap this technique can detect? .