Improving the Resolving Power of Ultraviolet to Near-Infrared Microwave Kinetic Inductance Detectors (Springer Theses)

This thesis represents a breakthrough in our understanding of the noise processes in Microwave Kinetic Inductance Detectors (MKIDs). While the detection of ultraviolet to near-infrared light is useful for a variety of applications from dark matter searches to biological imaging and astronomy, the performance of these detectors often limits the achievable science. The author’s work explains the limits on spectral resolution broadening, and uses this knowledge to more than double the world record spectral resolution for an MKID suitable for optical and near-IR astrophysics, with emphasis on developing detectors for exoplanet detection. The techniques developed have implication for phonon control in many different devices, particularly in limiting cosmic ray-induced decoherence in superconducting qubits. In addition, this thesis is highly accessible, with a thorough, pedagogical approach that will benefit generations of students in this area. Supervisor's Foreword 7 Acknowledgments 8 Publications 10 Contents 11 List of Terms 14 1 Introduction and Motivation 16 1.1 Exoplanet Spectroscopy 16 1.1.1 Direct Imaging 18 1.1.2 Detector Requirements 18 1.1.3 Commercial Detectors 20 1.2 Superconducting Detectors 21 1.2.1 Historic Examples 22 1.2.2 Microwave Kinetic Inductance Detectors 23 References 24 2 MKID Physics 29 2.1 Superconductivity 29 2.1.1 Density of States and Pairs 30 2.1.2 Gap Broadening 31 2.1.3 Proximity Effect 33 2.2 Superconducting Resonators 34 2.2.1 Quasiparticle Density 35 2.2.2 Complex Conductivity 35 2.2.3 Surface Impedance 36 2.2.4 Resonance Model 37 References 39 3 Data Analysis 43 3.1 Phase and Dissipation Coordinates 43 3.1.1 Coordinate Definition 43 3.1.2 Small Signal Limit 44 3.2 Photon Energy Estimation 45 3.2.1 Response Model 45 3.2.2 Noise Model 47 3.2.3 Maximum Likelihood Estimation 48 3.2.4 Filter Estimation 49 3.2.5 Estimator Variance 51 3.3 Correcting Coordinate Saturation 52 3.3.1 Alternative Phase and Dissipation Coordinates 52 3.3.2 Which Coordinates Do We Choose? 53 3.4 Attributions 54 References 54 4 Sensor Materials 57 4.1 Materials in Demonstrated Instruments 58 4.1.1 Titanium Nitride 58 4.1.2 Platinum Silicide 58 4.2 Hafnium 59 4.2.1 Resonator Properties 60 4.2.2 Full Array Measurements 63 4.3 Attributions 65 References 66 5 Detector and Readout Noise 69 5.1 Types of Noise 69 5.1.1 Thermal Noise 70 5.1.2 Amplifier Noise 71 5.1.3 Quantum Limited Noise 72 5.1.4 Two-Level System Noise 73 5.2 Reducing Amplifier Noise 75 5.2.1 Parametric Amplifiers 75 5.2.2 System Noise Characterization 77 5.2.3 Platinum Silicide Resolving Power Measurements 79 5.2.4 Hafnium Resolving Power Measurements 82 5.3 Attributions 83 References 84 6 Solving the Phonon Problem 86 6.1 Missing Energy 86 6.1.1 The Fano Limit 87 6.1.2 Hot Phonon Escape 87 6.2 Membrane Detectors 88 6.3 Phonon Blocking Layer 89 6.3.1 Effective Phonon Transmission 89 6.3.2 Low Debye Energy Interfaces 90 6.3.3 Device Description 92 6.3.4 Bilayer Proximity Effect and Tc 92 6.3.5 Resonator Measurements 94 6.3.6 Expected Phonon Trapping Improvement 95 6.4 Attributions 98 References 99 7 Conclusions 101 References 103 A Fourier Transform 104 A.1 Continuous Definitions 104 A.2 Discrete Definitions 105 References 106 B Resonator Equation Derivations 107 B.1 Asymmetric Shunt Resonator Equation 107 B.2 Nonlinear Resonance 109 B.3 I / Q Mixer Measurement and Calibration 112 B.4 Varying Circuit Parameters 114 References 117 C Y-Factor Measurement 119 C.1 Noise in Different Coordinates 119 C.2 Noise Measurement 121 C.3 Statistical and Systematic Errors 123 References 124 D Phonon Loss Calculations 125 D.1 Determining Jhigh 125 D.2 Determining Jlow 128 References 130 Curriculum Vitæ 132 Education 132 Honors and Awards 132 Publications 132