Design Considerations to Improving Sensitivity in Superspec: an Onchip KID-Based, Mm-Wave Spectrometer

Citation

Shiu, Corwin (2015) Design Considerations to Improving Sensitivity in Superspec: an Onchip KID-Based, Mm-Wave Spectrometer. Senior thesis (Major), California Institute of Technology. doi:10.7907/0XPB-W756. https://resolver.caltech.edu/CaltechTHESIS:01102018-113534206

Abstract

SuperSpec is an ultra-compact on-chip spectrometer for mm/submm astronomy. SuperSpec's compact size and wide spectral bandwidth will be uniquely powerful to perform multi-object spectroscopy for high redshift surveys, and for tomographic studies of the epoch of reionization (EoR). SuperSpec employs the use of kinetic inductance detectors (KID) to build highly multiplexed arrays. A full instrument of~ 500 channels can be lithographed on a few cm² of silicon.

In this thesis, we explored electromagnetic designs to improve sensitivity of KIDs. We show that we can reliably remove up to 753 of the current design's inductor volume to obtain improvements in sensitivities up a factor of four. We also explored two filter designs that can deliver higher power to the detectors. Our half-wave transmission line filters can only deliver up to 503 of power to the detectors. Both ring resonators and backshorted detectors can deliver unity power, however we found that the large coupling length needed in order to properly use ring resonators would be impractical in a. filterba.nk. Lastly we explored different filterbank designs. Multiple detectors read out together in a single channel has higher resolving power than single detector channels. Backshorted detectors offer higher resolving power than two paired detector channels, but under-performs three or more paired detector channels.