Senior Member, KICP
Assistant Professor, Department of Astronomy and Astrophysics
Ph.D., Physics, University of California, Berkeley, 2011
Detectors for astronomy at millimeter and submillimeter wavelength reached the background limit - the point at which photon counting statistics dominate instrumental noise - years ago. It's no longer possible to build a more sensitive detector. The best we can do is pack more detectors into a receiver. As a result, focal planes have grown from single hand-assembled pixels to lithographically defined arrays comprised of hundreds of detectors. To meet the science goals of the coming decade, future instruments will need to employ massive focal planes and hundred-kilopixel arrays.
While we can't build a more sensitive detector, there's still plenty of opportunity to build a better one. One strategy is to make each pixel do more: using on-chip microwave circuits and broad-band antennas and optics to enable multichroic detectors and integral-field spectrometers, packing more bandwidth into each physical device. Alternatively, we can make each pixel cheaper, more robust, and easier to read out with multiplexed hardware.
Our lab is working on both goals. Using modern thin-film processes and electromagnetic simulation software, we're working to move optical elements on-chip, replacing bulky and expensive mechanical hardware with planar circuits. When it comes to simple fabrication and low cost multiplexing, few technologies can compete with kinetic inductance detectors (KIDs). These pair-breaking superconducting detectors can be fabricated in a few layers and read-out at densities of thousands of channels per coax cable, and are approaching the sensitivity required for even low-loading applications at mm wavelengths.
Here are some of the projects that we're currently collaborating on:
- SuperSpec is a novel, ultra-compact spectrograph-on-a-chip for millimeter and submillimeter wavelength astronomy. Its very small size, wide spectral bandwidth, and highly multiplexed detector readout will enable construction of powerful multibeam spectrometers for high-redshift observations.
- Our new CMB KIDs program is working to develop background-limited, multi-band, dual-polarized, antenna-coupled KID arrays optimized for the next generation of ground-based Cosmic Microwave Background (CMB) experiments. By combining the design flexibility, multiplexing density, and low-cost readout enabled by the use of hundred megahertz lumped element titanium nitride KIDs with state of the art broad band lithographic antennas and microstrip band-defining features, this technology will enable future CMB focal planes that simple to fabricate and can be read out at very low cost.
- SPT-3G, is the the third generation receiver for the 10 meter South Pole Telescope. SPT-3G and enables high signal-to-noise measurements of CMB B-mode polarization. This will lead to precise (∼0.06 eV) constraints on the sum of neutrino masses with the potential to directly address the neutrino mass hierarchy. It will allow a separation of the lensing and inflationary B-mode power spectra, improving constraints on the amplitude and shape of the primordial signal. Other science goals include the precise measurement of small-scale temperature anisotropy which will provide new constraints on the duration of the epoch of reionization, and information about large scale structure, galaxy cluster abundance based upon joint analysis with the overlapping Dark Energy Survey (DES).
- TIME, the Tomographic Ionized-Carbon Mapping Experiment (TIME) and the pathfinder project, TIME-Pilot, are a proposed imaging spectrometers that will measure reionization and large scale structure at redshifts 5-9.