title: Optical performance of an ultra-sensitive horn-coupled transition-edge-sensor bolometer with hemispherical backshort in the far infrared.
abstract: The next generation of far infrared space observatories will require extremely sensitive detectors that can be realized only by combining extremely low intrinsic noise with high optical efficiency. We have measured the broad-band optical response of ultra-sensitive transtion edge sensor (TES) bolometers (NEP≈2aW/Hz) in the 30-60-μm band where radiation is coupled to the detectors with a few-moded conical feedhorn and a hemispherical backshort. We show that these detectors have an optical efficiency of 60% (the ratio of the power detected by the TES bolometer to the total power propagating through the feedhorn). We find that the measured optical efficiency can be understood in terms of the modes propagating through the feedhorn with the aid of a spatial mode-filtering technique.
authors.affiliation: SRON Netherlands Institute for Space Research, Postbus 800, 9700 AV Groningen, The Netherlands.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Audley
authors.affiliation: SRON Netherlands Institute for Space Research, Postbus 800, 9700 AV Groningen, The Netherlands.
authors.forename: Gert
authors.initials: G
authors.lastname: de Lange
authors.affiliation: SRON Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands.
authors.forename: Jian-Rong
authors.initials: JR
authors.lastname: Gao
authors.affiliation: SRON Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands.
authors.forename: Pourya
authors.initials: P
authors.lastname: Khosropanah
authors.affiliation: SRON Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands.
authors.forename: Richard
authors.initials: R
authors.lastname: Hijmering
authors.affiliation: SRON Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands.
authors.forename: Marcel
authors.initials: M
authors.lastname: Ridder
authors.affiliation: School of Physics and Astronomy, Cardiff University, Queen's Buildings, The Parade, Cardiff CF24 3AA, United Kingdom.
authors.forename: Philip D
authors.initials: PD
authors.lastname: Mauskopf
authors.affiliation: School of Physics and Astronomy, Cardiff University, Queen's Buildings, The Parade, Cardiff CF24 3AA, United Kingdom.
authors.forename: Dmitry
authors.initials: D
authors.lastname: Morozov
authors.affiliation: Department of Experimental Physics, Maynooth University, Maynooth, County Kildare W23 F2H6, Ireland.
authors.forename: Neil A
authors.initials: NA
authors.lastname: Trappe
authors.affiliation: Department of Experimental Physics, Maynooth University, Maynooth, County Kildare W23 F2H6, Ireland.
authors.forename: Stephen
authors.initials: S
authors.lastname: Doherty