Quantum Limited SIS Receiver Technology for the Detection of Water Isotopologue Emission from Comets

NASA’s Planetary Science Decadal Survey has concludedthat isotopic measurements of cometary water vapor are ameans to unraveling the mysteries involving the origin of Earth‘swater and the evolution of our solar system. To support this, arecent Jet Propulsion Laboratory (JPL) internal research programhas developed quantum limited Superconductor InsulatorSuperconductor (SIS) receivers in the important 500􀀀600 GHzsubmillimeter frequency band. These instruments can be used todetect the HDO ground state (110-101), H162 O ortho ground-state(110-101), and the oxygen isotopologues H172 O, and H182 O withexquisite sensitivity.To achieve the presented results we have investigated AluminumOxide (AlOx) and Aluminum Nitride (AlNx) barrierSIS tunnel junction mixers on 6 m Silicon-on-Insulator (SOI)substrate. The AlOx and AlNx junction mixer blocks utilizediagonal and smooth-profile conical horns respectively. In bothcases a commercial 4-8 GHz Intermediate Frequeny (IF) lownoise amplifier (LNA) has been integrated into the mixer block.The AlOx (low current density) barrier SIS junctions werefabricated with 2 m gold beamlead technology, whereas inthe case of the AlNx SIS tunnel junction we use capacitiveRF decoupling tabs. The latter approach simplifies fabrication,increases yield, eases the mounting process, and facilitates scalingto higher frequencies.For an actual flight mission, with operation 4.2 K, the allowedheat dissipation of the mixer integrated low noise amplifierneeds to be minimized. In this paper we also investigate thereceiver sensitivity as a function of LNA DC power consumption.We find that the DC power consumption of the low noise amplifiercan be reduced to 1.6 mW with minimal loss in sensitivity. It isanticipated that continued InP HEMT development for quantumcomputer applications are likely to reduce the required LNA power dissipation even further.