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

对宇宙微波背景辐射（CMB）线偏振的测量提供了对早期宇宙的独特探测。目前最成功的现代宇宙学模型包括大爆炸后不久的时空快速膨胀时期。在暴胀时期激发的引力波在宇宙中传播，并在很晚的时候相互作用，使CMB呈现出独特的偏振模式。这种引力波信号的探测将对宇宙学和高能物理学产生深远的影响。它不仅将暴胀确立为一种物理现实，而且还将检验能量超过10^15 GeV的物理学，这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认识。宇宙微波背景辐射中预测的偏振信号很弱，而且它的测量因银河系更明亮的辐射而变得复杂。 为了有效地分离这两种成分，测量必须准确，并在很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时间尺度（~100 Hz）上在相反的偏振状态之间被电“斩波”，时间尺度（~100 Hz）比与观察条件相关的时间尺度短得多。 迄今为止，这些集成偏振计还缺少一个关键部件：能够在低温下长时间工作的低电容、低插入损耗开关。PI的Barker和Kogut将要开发的MEMS器件是微机电开关，它似乎满足完成这些“芯片上偏振计”的所有必要标准。 这项专门工作的核心是弗吉尼亚大学微加工实验室和美国宇航局戈达德航天飞行中心探测器开发实验室的最先进的开发设施的结合。 这些设施共同实现了在高达250 GHz的频率下运行的复杂电气网络的制造和低温测试。超越了获得有关我们宇宙早期历史的基本信息的技术开发，根据该奖项开展的工作将涉及mm科学和工程领域的研究生和本科生，波仪器和产生新的技术，将有利于遥感和宽带通信领域的新兴应用。

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.