The most promising method for detecting primordial gravitational waves lies in the B-mode polarization of the cosmic microwave background, or CMB. A measurement of these B-modes would reveal the first evidence for quantum gravity and determine the energy scale of inflation. However, polarized foreground emission from synchrotron radiation and dust in our galaxys magnetic field are sources of significant contamination for CMB B-mode polarization maps. I propose to develop high-precision photometric calibration technology in order to make the highest possible quality foreground-cleaned polarization maps of the CMB. I will build and characterize a precision Fourier Transform Spectrometer (FTS) with a novel optical coupling scheme that will enable on-site measurements of Advanced ACTPols detectors spectral responses. I will develop new anti-reflection coating technology for optical systems to ensure precise calibration. With my calibration in hand, I will then produce foreground-separated polarization maps which will be used to place constraints on inflation, neutrinos and dark energy. The technology I develop will be applicable to all suborbital and space-based CMB, millimeter wave, and submillimeter wave experiments. My work aligns with NASAs goals outlined in the Science Instruments, Observatories, and Sensor Systems Roadmap (TA08.1.4 and TA08.2.2), Materials, Structures, Mechanical Systems, and Manufacturing Roadmap (TA12.1.4), Physics of the Cosmos Program, and Cosmic Origins Program.