Collaborative Research: RF-MEMS Phase Modulators for Millimeter-wave Polarimeter Array

测量宇宙微波背景（CMB）的线极化提供了一个独特的探索早期宇宙。目前最成功的现代宇宙学模型包括大爆炸后不久时空快速膨胀的时代。在这个暴胀时期激发的引力波在宇宙中传播，并在更晚的时间相互作用，给CMB带来了独特的极化模式。探测到这种引力波特征将对宇宙学和高能物理学产生深远的影响。它不仅可以将暴胀作为一种物理现实，而且可以在10^15 GeV以上的能量下进行探测，比粒子加速器所能达到的能量高出12个数量级，从而对大统一和量子引力的本质产生新的见解。CMB中预测的极化信号很弱，而且由于银河系发射的更亮的辐射，测量变得复杂。为了有效地分离这两种成分，测量必须准确，并且在较宽的频率范围内进行。有效测量CMB偏振的最有前途的技术之一是构建多像素集成偏振计阵列，其中每个通道中的信号在相对偏振状态之间被电“斩”，时间尺度（~100 Hz）比观测条件短得多。迄今为止，这些集成偏振计缺乏一个关键项目：低电容，低插入损耗开关，可以在低温下长时间工作。由PI的Barker和Kogut开发的MEMS器件是微机电开关，似乎满足完成这些“片上偏振计”的所有必要标准。这项专业工作的核心是弗吉尼亚大学微加工实验室最先进的开发设施和美国宇航局戈达德太空飞行中心探测器开发实验室的结合。这些设施共同实现了在高达250 GHz频率下运行的复杂电气网络的制造和低温测试。除了开发一种获取宇宙早期历史基本信息的技术之外，根据该奖项开展的工作将涉及毫米波仪器科学和工程专业的研究生和本科生，并开发将有利于遥感和宽带通信领域新兴应用的新技术。

Measurements of the linear polarization of the cosmic microwave background (CMB) offer a unique probe of the early universe. The currently most-successful model of modern cosmology includes an epoch of rapid expansion of space-time shortly after the Big Bang. Gravity waves, excited during this inflationary epoch, propagate through the universe and interact at much later times to impart a distinctive polarization pattern to the CMB. Detection of this gravity-wave signature would have profound consequences for both cosmology and high-energy physics. Not only would it establish inflation as a physical reality, a detection would test physics at energies above 10^15 GeV, more than 12 orders of magnitude beyond what is accessible in particle accelerators, yielding new insight into the nature of Grand Unification and quantum gravity.The predicted polarization signal in the CMB is weak and its measurement complicated by much brighter emission from the Milky Way galaxy. To effectively separate these two components, measurements must be accurate and made over a wide range in frequency. One of the most promising techniques for efficiently measuring the polarization of the CMB is in constructing many-pixel, integrated polarimeter arrays in which the signal in each channel is "chopped" electrically between opposing polarization states on time scales (~100 Hz) much shorter than those associated with the observing conditions. To date, these integrated polarimeters have lacked one key item: low-capacitance, low-insertion loss switches that can operate at cryogenic temperatures for long periods of time.The MEMS devices to be developed by PI's Barker and Kogut are Micro-Electro-Mechanical switches that appear to satisfy all of the necessary criteria for completing these "polarimeters on a chip". Central to this specialized effort is the combination of state-of-the-art development facilities at the University of Virginia Microfabrication Laboratories and the Detector Development Laboratory at NASA's Goddard Space Flight Center. Together these facilities enable fabrication and cryogenic testing of sophisticated electrical networks operating at frequencies up to 250 GHz.Going beyond the development of a technique for obtaining fundamental information about the early history of our Universe, the work to be carried out under this award will involve graduate and undergraduate students in the science and engineering of mm-wave instrumentation and produce new technologies that will benefit emerging applications in the fields of remote sensing and wideband communications.