Jeffrey A. Stern Passed Away

October 11, 2013 (PO27). Dr. Jeffrey A. Stern was born on September 16, 1961, and passed away on October 11, 2013, at the age of 52, after a year-long battle with cancer.

Jeff received his B.S. physics degree from Rensselaer Polytechnic Institute in 1983 and his Ph.D. from California Institute of Technology in 1991. He spent his entire career at the Caltech Jet Propulsion Laboratory in Pasadena, CA. During his tenure at JPL, he made significant contributions to the development of superconducting sensors. He fabricated, tested, and space-qualified superconductor–insulator–superconductor (SIS) mixer chips, an enabling technology for band 5 (1140–1250 GHz) of the Heterodyne Instrument for the Far-Infrared (HIFI) on the Herschel Space Observatory. HIFI band 5 included some key spectral lines that have had a major impact on understanding of the interstellar medium (ISM) and astrochemistry. Possibly the most important is the ground state transition of hydrogen fluoride (HF). A large number of Herschel studies confirm that essentially all flourine in the diffuse ISM is in the form of hydrogen fluoride, HF. Consequently, this 1232 GHz transition, measured using band 5, can be an accurate tracer of the total column density of clouds. HF has been exploited in studies of the Milky Way and is now being used in observations of external galaxies. Also, Band 5 enabled detection of new species critical for understanding the production of water in the ISM such as H2O+, and made major contributions to unraveling the ortho-to-para ratio of the water molecule, giving strong indications about the conditions for the formation of water in space.

After delivering HIFI band 5 mixers, Jeff pioneered the use of phonon-cooled niobium nitride (NbN) mixers and fabrication of THz waveguide components using lithographic techniques. These technologies enabled new instrument concepts proposed for NASA's sub-orbital programs and follow-on space missions after HIFI. Concurrently with the THz mixer development, Jeff began work on new detectors for optical communications. Jeff was the first person in the US (2004) to make a functional superconducting nanowire single photon detector (SNSPD); the first person to fabricate a functional SNSPD in NbTiN (2006) and the first to fabricate arrays (4 to 16 pixels, 2005-2007). From 2012-2013, Jeff designed and fabricated fiber optic coupled SNSPDs from tungsten silicide (WSi) with the highest efficiency demonstrated to date (93%), 12-pixels arrays used in 2012 to establish an optical communications link with the Lunar Atmosphere and Dust Environment Explorer (LADEE) spacecraft orbiting the moon. His last accomplishment was a 64-pixel free space coupled SNSPD with an active area over 100 times greater than other state-of-the-art devices designed to be mounted on large telescope such as the 5 m Hale telescope at Palomar in California that can be used for optical communication with spacecraft around other planets, for observing ultrafast astrophysical events and for experimentally measuring quantum mechanical effects over large distances. Jeff Stern's innovations and technology leadership have led to a world-leading team at NASA developing optical detectors for space applications with near perfect efficiency, near zero noise, and high (sub-nanosecond) photon arrival timing resolution.

Outside of his profession, Jeff Stern was an avid participant in outdoor activities, including skiing, hiking, camping, rock climbing, swimming, scuba diving. He loved to cook and was a self-professed "foodie" who delighted in locating and trying new restaurants. He was also an avid gamer right up until the time he passed. Jeff was devoted to his family and is survived by Allison, his wife of 23 years, and his son Noah (19) and daughter Maddy (16).