I am interested in enabling the next generation of precision cosmological measurements in order to better understand the history and content of the universe. I focus on making millimeter-wave maps of the sky, which contain both the Cosmic Microwave Background (or CMB), and red-shifted spectral emission lines from gas clouds in far-away galaxies. Observations of the CMB can be used to probe inflationary theories and test for beyond-the-Standard-Model physics; measurements of spectral lines at high redshifts can trace the history of galaxy formation and large-scale structure. My PhD work is aimed at improving the accuracy and precision of these maps by calibrating the frequency response of microwave cosmological instruments to unprecedented (sub-percent) precision. Because my work touches on a wide range of disciplines, including optics, detector design, electronics, and astrophysics, the HKLF is an ideal space for me to share my research and learn from other young scientists. My collaborations thus far have mostly been limited to within the U.S., and therefore I particularly look forward to meeting and working with scientists from Hong Kong and the rest of the world.

Millimeter-wave observations of the sky demand precisely calibrated detector bandpasses to extract meaningful scientific data from on-sky measurements. This is because the millimeter-wave frequency range overlaps with that of a number of astrophysical foregrounds, including synchrotron and thermal dust radiation, which must be modelled & removed based on their different frequency dependencies. Current bandpass calibration techniques have limited precision due to systematic errors stemming from standing-wave interference effects and position-dependent spectral shifts. I present the design of a robotically-controlled optical coupling system capable of reducing these systematic errors to the sub-percent level. My design relies on the introduction of off-axis aspherical mirrors to match the beam of the telescope receiver while avoiding lens-based interference effects. It also incorporates a robotic stage to move the mirrors in three orthogonal directions in order to minimize positional spectral shifts. Once deployed, this bandpass calibration technology will enable the best-ever foreground-separated maps of the Cosmic Microwave Background, and some of the first well-calibrated maps of spectral line emission from the epoch of reionization.