An SNS antenna-coupled direct detector of submillimeter radiation D. Chouvaev * , L. Kuzmin Department of Microelectronics and Nanoscience, Chalmers University of Technology, SE-412 96 G oteborg, Sweden Abstract We present our recent results in development of a direct detector of submillimeter waves bolometer) based on a mesoscopic power sensor coupled to an integrated antenna. An electrical noise equivalent power of 5 10 18 W= Hz p at 0.1 K has been demonstrated in dc measurement. A cryogenic system for optical evaluation of the detector has been designed and is currently being built. Ó 2001 Elsevier Science B.V. All rights reserved. PACS: 85.25.Pb; 95.55.-n Keywords: Bolometer; Far infrared; Andreev re¯ection; Tunnel junction; Hot electron 1. Introduction Recently there has been increased interest to applying mesoscopic structures for detection of electromagnetic radiation in the submillimeter and far-infrared ranges [1±3]. These intermediate fre- quency ranges have for a long time been poorly covered by sensitive detectors. The mesoscopic sensors are expected to replace present black-body bolometers with noise equivalent power NEP) sensitivity) NEP 10 17 W= Hz p at 0.1 K and time constant s 10 2 s. Better sensitivity, faster reaction time, and, probably the most important, feasibility of building large imaging detector ar- rays are being promised with the new detectors. Radio astronomy is currently the most demanding application for these detectors. We are developing the detector scheme proposed in Ref. [1] ± a nor- mal metal hot-electron bolometer Fig. 1) [4]. The operating principle of the detector is based on measuring electron temperature in the normal metal N) island of a superconductor-normal metal-superconductor SNS) system, where the electrons are excited by heat from a high-fre- quency current induced in the antenna, and trap- ped by Andreev re¯ections. The con®ned electron gas inside the N-island can be in equilibrium at temperature dierent from the lattice temper- ature due to that the electron-phonon inelastic interaction time at low temperatures s ep 10 5 s at T 0:1 K) is much longer than the electron± electron inelastic interaction time on the order of 10 9 s [5]). The electron temperature is deduced from the thermal smearing of the IV-curve of two NIS tunnel junctions in series, which have the heat-absorbing N-island as their N-elec- trode Fig. 1). The moderately thin normal-metal ®lms still show electron±phonon relaxation time s ep T 3 and the cooling rate for electrons at Physica C 352 2001) 128±130 www.elsevier.nl/locate/physc * Corresponding author. Fax: +46-31-772-3471. E-mail address: chouvaev@fy.chalmers.se D. Chouvaev). 0921-4534/01/$ - see front matter Ó 2001 Elsevier Science B.V. All rights reserved. PII:S0921-453400)01707-X