We describe the design, fabrication, and laboratory-demonstration of a novel dual-polarized multichroic antenna-coupled Transition Edge Sensor (TES) bolometer. Each pixel separates the incident millimeter radiation into two linear polarization channels as well as several frequency channels (bands). This technology enables us to realize bolometer arrays for Cosmic Microwave Background (CMB) polarimetry measurements that map the sky at multiple colors while simultaneously boosting the optical throughput over what would have been attained from arrays of single-frequency channel detectors. Observations at multiple frequency channels are important for differentiating polarized galactic foregrounds and atmospheric fluctuations from the CMB.

Each pixel couples free-traveling radiation onto lithographed microstrip transmission lines prior to the bolometers using a dual-polarized broadband antenna known as a sinuous antenna. The transmission lines are integrated onto the back of the antenna arms and the antennas are in direct contact with an extended-hemispherical lens. We show measurements of scale model (4-12GHz) and to-scale (80-240Hz) antennas to demonstrate high antenna-gain, low cross-polarization contamination, and efficient coupling over a 1-2 octave bandwidth.

We have developed microstrip circuits that divide the antenna's wide bandwidth into smaller channels. In one scheme, two or three frequency channels can be extracted from the antenna's received power using microstrip circuits known as diplexers and triplexers. These avoid atmospheric spectral lines and are well suited to terrestrial observations. We can also partition this bandwidth into contiguous bands using cochlear channelizers inspired by the physiology of the human ear; this design is most advantageous for satellite missions where there are no concerns about atmospheric contamination. We present design methodologies for these circuits and show measurements of prototypes coupled to TES bolometers to verify acceptable performance. We also describe the fabrication of a broadband anti-reflection coating for the contacting lenses and demonstrate that lens-coupled sinuous pixels receive more power with the coatings than without. Finally, we remark on the last un-resolved challenge of forming symmetric beams and balun designs that may help form patterns more useful for polarimetry.

This technology is a candidate for use in the Polarbear ground-based experiment. By packing more detectors into the focal-plane than can be done with monochromatic pixels, multichroic pixels will allow Polarbear to map the sky much faster. This technology is also candidate for future space-based missions as well, where multhchroic pixels will allow a less massive payload and hence a lower cost mission. Finally, we envision using arrays of similar pixels in sub-millimeter observations of high-redshift galaxy clusters as well (e.g.example Sunyaev-Zeldovich Effect measurements). However, we require more sophisticated lithography and etching techniques to shrink these pixels to a size suitable for such wavelengths.

Characterization of the Cosmic Microwave Background (CMB) B-mode polarization signal will test models of inflationary cosmology, as well as constrain the sum of the neutrino masses and other cosmological parameters. The low intensity of the B-mode signal combined with the need to remove polarized galactic foregrounds requires a sensitive millimeter receiver and effective methods of foreground removal. Current bolometric detector technology is reaching the sensitivity limit set by the CMB photon noise. Thus, we need to increase the optical throughput to increase an experiment's sensitivity. To increase the throughput without increasing the focal plane size, we can increase the frequency coverage of each pixel. Increased frequency coverage per pixel has additional advantage that we can split the signal into frequency bands to obtain spectral information. The detection of multiple frequency bands allows for removal of the polarized foreground emission from synchrotron radiation and thermal dust emission, by utilizing its spectral dependence. Traditionally, spectral information has been captured with a multi-chroic focal plane consisting of a heterogeneous mix of single-color pixels. To maximize the efficiency of the focal plane area, we developed a multi-chroic pixel. This increases the number of pixels per frequency with same focal plane area.

We developed multi-chroic antenna-coupled transition edge sensor (TES) detector array for the CMB polarimetry. In each pixel, a silicon lens-coupled dual polarized sinuous antenna collects light over a two-octave frequency band. The antenna couples the broadband millimeter wave signal into microstrip transmission lines, and on-chip filter banks split the broadband signal into several frequency bands. Separate TES bolometers detect the power in each frequency band and linear polarization. We will describe the design and performance of these devices and present optical data taken with prototype pixels and detector arrays. Our measurements show beams with percent level ellipticity, percent level cross-polarization leakage, and partitioned bands using banks of two and three filters. We will also describe the development of broadband anti-reflection coatings for the high dielectric constant lens. The broadband anti-reflection coating has approximately 100% bandwidth and no detectable loss at cryogenic temperature.

We will describe a next generation CMB polarimetry experiment, the POLARBEAR-2, in detail. The POLARBEAR-2 would have focal planes with kilo-pixel of these detectors to achieve high sensitivity. We'll also introduce proposed experiments that would use multi-chroic detector array we developed in this work. We'll conclude by listing out suggestions for future multichroic detector development.

Transition edge sensor (TES) bolometer technology has been at the core of advancements

in experimental cosmic microwave background (CMB) science for the

past few decades. Theoretical and experimental work has built a robust model of

the universe. Despite tremendous progress, there are several key pieces of experimental

evidence missing to complete our understanding of the universe. This dissertation

covers the work done by Benjamin Grey Westbrook at the University of California

Berkeley between 2007 and 2014. It is centered around the use of spider-web absorber

transition edge sensor (SWATES) bolometers to study the cosmos by the

Atcama Pathnder Experiment - Sunyaev Zel'dolvich (APEX-SZ) and the E and

B Experiment (EBEX). Both of which help complete our model of the universe in

complimentary ways.

APEX-SZ is a ground-based experiment that made observations of galaxy clusters

via the Sunyaev-Zel'dovich Eect from the Chajnantor Plateau in Northern Chile

from 2005 to 2010. It observed galaxy clusters at 150 GHz with 300 SWATES detectors

with a resolution of 10. Galaxy clusters are the largest gravitationally bound

objects in the present day universe and are excellent for studying the properties of

the universe. The primary goal of APEX-SZ was to understand the complex physics

of galaxy clusters. By understanding their composition, number density, and evolution

we can better our understanding of the evolution of the universe into its present

state.

EBEX is a balloon-borne experiment that made observations of the CMB and

cosmic foreground during a science

ight from the Long Duration Balloon (LDB)

facility outside of McMurdo Station, Antarctica over the 2012-2013 austral summer.

It made observations of 6000 square degrees of sky using 872, 436, and 256 SWATES

bolometers at 150, 250, and 410 GHz detectors (respectively) with 80 resolution

We present the \pb experiment and its measurement of the B-mode power spectrum. \pb is a millimeter wave telescope that is measuring the Cosmic Microwave Background (CMB) polarization, using large format arrays of photon noise limited Transition-Edge Sensor (TES) bolometers. The instrument observes from the Atacama Desert at 5.2km in elevation with a 2.5m primary aperture telescope. This telescope has sufficient angular resolution (3.5' FWHM) to resolve the gravitational lensing features of the CMB, a new channel for obtaining information on fundamental physics such as the sum of the mass of neutrinos.

This dissertation describes the design, integration and results of the first season of \pb observations. The receiver observed for 1 year with a noise-equivalent temperature (NET) of $22.8\mu K \sqrt{s}$ and mapped a 30 square degree area of the CMB, obtaining evidence for gravitational lensing in the BB power spectrum at a significance of $2\sigma$.

New technology has rapidly advanced the field of observational cosmology over the last 30 years. This trend will continue with the development of technologies to measure the Cosmic Microwave Background (CMB) polarization. The B-mode component of the polarization map will place limits on the energy scale of inflation and the sum of the neutrino masses. This thesis describes the \pb instrument which will measure the CMB polarization anisotropy to unprecedented sensitivity. POLARBEAR-I is currently observing, and an upgraded version, POLARBEAR-II, is planned for the future.

The first version of the experiment, POLARBEAR-I, is fielding several new technologies for the first time. POLARBEAR-I has high sensitivity due to its detector count. It employs a 1274 detector Transition-Edge Sensor (TES) bolometer array. The bolometers are coupled to a planar array of polarization sensitive antennas. These antennas are lithographed on the same substrate as the TES detectors, allowing on-chip band defining filters between the antenna and detector. The focal plane is composed of seven hexagonal detector modules. This modular scheme can be extended to create larger focal plane arrays in the future. POLARBEAR-I is observing at a single band near 150 GHz, the peak in the CMB blackbody curve.

The lenslet antenna coupled detector technology, fielding for the first time in POLARBEAR-I, is naturally scalable to larger arrays with multi-chroic pixels. This broadband technology will have higher sensitivity and better capability for astronomical foreground contaminant removal. The antenna geometry can be changed to receive a wider frequency bandwidth. This bandwidth can be broken into multiple frequency bands with the on-chip band defining filters. Each band will be read out by one TES detector. A dual band instrument, \pbtwo, is in development with bands at 90 and 150 GHz.

One challenge for all CMB polarization measurements is minimization of systematic errors. One source of error is polarized reflections off of the refractive optics inside the receiver. Specifically, the antenna-coupled detector scheme relies on a high dielectric lenslet for each pixel on the focal plane. A large portion of this thesis discusses development of anti-reflection (AR) coatings for the high curvature lenslet surface. The AR coating technologies discussed are also applicable to other optical elements, such as reimaging lenses and half-wave plates. A single layer coating is used on the \pbone lenslet array, and a two layer coating is presented for use in \pbtwo. The two layer coating method can be extended to wider bandwidth AR coatings.

Cosmic microwave background (CMB) experiments have paved the way towards a greater understanding of early universe physics and building a standard model of cosmology. In this dissertation, we report on the development, integration, testing, and deployment of the ultra-high-frequency small aperture telescope for the Simons Observatory (SO). We also discuss development and optimization of detector arrays for CMB experiments, and describe the SO low-frequency wafers in detail. This work also directly impacts developments for CMB-S4 and LiteBIRD. We also discuss the ongoing calibration and scan strategy efforts in SO as the experiment moves towards initial science observations.

POLARBEAR is a Cosmic Microwave Background (CMB) polarization experiment that will measure the CMB polarization angular power spectrum with unprecedented precision, searching for evidence of inflationary gravitational waves and the gravitational lensing of the CMB polarization by large scale structure. This dissertation presents an overview of the design of the instrument, focusing on the design and fabrication of the focal plane, and presents the results of some tests of instrument performance, both in the laboratory and from the initial engineering deployment.

The structure of this thesis is as follows: Chapter 1 introduces the theoretical constructs used to describe the CMB polarization anisotropies, and the state of measurements in the field. Chapter 2 gives an overview of the choices made in the instrument design. Chapter 3 discusses the fundamental limits to the sensitivity of bolometric detectors, and chapter 4 explains the design choices involved in populating the focal plane with detectors. Chapter 5 describes the details of the detector architecture and fabrication, and chapter 6 the details of selecting the spectral band of the detectors. Finally, chapter 7 goes through some results obtained before and during the POLARBEAR engineering run in 2010, and comments on the work to be done before the Chilean deployment.

We report on the development of multiscale multichroic focal planes for measurements of the cosmic microwave background (CMB). A multichroic focal plane, i.e., one that consists of pixels that are simultaneously sensitive in multiple frequency bands, is an efficient architecture for increasing the sensitivity of an experiment as well as for disentangling the contamination due to galactic foregrounds, which is increasingly becoming the limiting factor in extracting cosmological information from CMB measurements. To achieve these goals, it is necessary to observe across a broad frequency range spanning roughly 30-350 GHz. Depending on the foreground complexity, it may become necessary to observe across an even larger range. For this purpose, the Berkeley CMB group has been developing multichroic pixels consisting of planar superconducting sinuous antennas coupled to extended hemispherical lenslets, which operate at sub-Kelvin temperatures. The sinuous antennas, microwave circuitry and the transition-edge-sensor (TES) bolometers to which they are coupled are integrated in a single lithographed wafer.

We describe the design, fabrication, testing and performance of multichroic pixels with bandwidths of 3:1 and 4:1 across the entire frequency range of interest. Additionally, we report on a demonstration of multiscale pixels, i.e., pixels whose effective size changes as a function of frequency. This property keeps the beam width approximately constant across all frequencies, which in turn allows the sensitivity of the experiment to be optimal in every frequency band. We achieve this by creating phased arrays from neighboring lenslet-coupled sinuous antennas, where the size of each phased array is chosen independently for each frequency band. We describe the microwave circuitry in detail as well as the additional benefits of a multiscale architecture, e.g., mitigation of beam non-idealities, reduced readout requirements and polarization-wobble cancellation. Finally, we discuss the design and fabrication of the detector modules and focal-plane structures including cryogenic readout components, which enable the integration of our devices in current and future CMB experiments.

We describe the development of a novel millimeter-wave cryogenic detector. The device integrates a planar antenna, superconducting transmission line, bandpass filter, and bolometer onto a single silicon wafer. The bolometer uses a superconducting Transition-Edge Sensor (TES) thermistor, which provides substantial advantages over conventional semiconductor bolometers. The detector chip is fabricated using standard micro-fabrication techniques.

This highly-integrated detector architecture is particularly well-suited for use in the development of polarization-sensitive cryogenic receivers with thousands of pixels. Such receivers are needed to meet the sensitivity requirements of next-generation cosmic microwave background polarization experiments.

The design, fabrication, and testing of prototype array pixels are described. Preliminary considerations for a full array design are also discussed. A set of on-chip millimeter-wave test structures were developed to help understand the performance of our millimeter-wave microstrip circuits. These test structures produce a calibrated transmission measurement for an arbitrary two-port circuit using optical techniques, rather than a network analyzer. Some results of fabricated test structures are presented.

We present the design and characterization of the POLARBEAR experiment. POLARBEAR is a millimeter-wave polarimeter that will measure the Cosmic Microwave Background (CMB) polarization. It was designed to have both the sensitivity and angular resolution to detect the expected B-mode polarization due to gravitational lensing at small angular scales while still enabling a search for the degree scale B- mode polarization caused by inflationary gravitational waves. The instrument utilizes the Huan Tran Telescope (HTT), a 2.5-meter primary mirror telescope, coupled to a unique focal plane of 1,274 antenna-coupled transition-edge sensor (TES) detectors to achieve unprecedented sensitivity from angular scales of the experiment's 4 arcminute beam to several degrees.

This dissertation focuses on the design, integration and characterization of the cryogenic receiver for the POLARBEAR instrument. The receiver cools the ∼ 20 cm focal plane to 0.25 Kelvin, with detector readout provided by a digital frequency- multiplexed SQUID system. The POLARBEAR receiver was been successfully deployed on the HTT for an engineering run in the Eastern Sierras of California and is currently deployed on Cerro Toco in the Atacama Dessert of Chile. We present results from lab tests done to characterize the instrument, from the engineering run and preliminary results from Chile.