20th IMEKO TC4 International Symposium and 18th International Workshop on ADC Modelling and Testing Research on Electric and Electronic Measurement for the Economic Upturn Benevento, Italy, September 15-17, 2014 A Superconducting Bolometer for Terahertz Radiation Detection Guido Torrioli 1 , Sara Cibella 1 , Fabio Chiarello 1 , Roberto Leoni 1 , Pasquale Carelli 2 , Roberto Casini 3 , Giorgio Dall’Oglio 4 , Licia Pizzo 4 and Lucia Sabbatini 5 1 Istituto di Fotonica e Nanotecnologie, CNR, Via Cineto Romano 42, 00156 Roma, Italy, guido.torrioli@ifn.cnr.it 2 Dipartimento di Scienze Fisiche e Chimiche,Università dell’ Aquila, Italy, 3 Università di Napoli “Federico II”Dipartimento di Fisica 4 Dipartimento di Fisica, Università di Roma Tre, Roma, Italy 5 INFN, Frascati, Italy Abstract – In this work we present the progress on the realization of a superconducting microbolometer sensible to the THz radiation. The operation of this detector is based on an integrated antenna coupled to a suspended strip of superconducting material. The bolometer works anywhere in the temperature range 2-7 K which can be easily reached in helium bath cryostats or closed-cycle cryocoolers. We also report on two possible applications we are working on, one related to a system for homeland security and the other one to astrophysical observations. I. INTRODUCTION In the last decade there has been an increasing interest in applications in terahertz sensing, spectroscopy and imaging that can be applicable in several fields such as astrophysics and atmospheric science, biomedical imaging, information and communication technology, non destructive evaluation, detection of concealed weapons, drugs, and explosives and so forth. The interest in applications in this region of the electromagnetic spectrum, which was characterized by a relative lack of convenient devices, has been triggered by the recent appearance of practical devices capable of both generating and detecting the radiation. The recent development of solid state sources such as Quantum Cascade Lasers (QCL) emitting in the THz region, for example, is giving a boost to the development of new applications as they improve their characteristics in terms of emitted power and operating temperature. There has been a large activity in recent years also concerning the development of the THz detectors. Here we present the performances of a superconducting bolometer with high sensitivity, ease to use and of an optimized readout electronics, called SHAB (Superconducting Hot-spot Air- bridge Bolometer) II. THE BOLOMETER’S OPERATING PRINCIPLES The Bolometer structure is based on a design first introduced by Luukanen and Pekola in 2003 [1]. It consists of a microscopic narrow Nb strip where, in order to improve its sensitivity, the thermal isolation is enhanced by removing the physical contact with the substrate, creating a free standing bridge structure. The application of a voltage bias to this superconducting structure causes the formation of a hot spot in the middle of the strip where the superconductor switches to the normal state. The suspended strip acts as a thermometer since the incoming radiation energy is dissipated in the hot spot region with a consequent modulation of its size. This results in a modulation of its resistance and, in turn, in a modulation of the current that flows as a result of the voltage bias. The recording of this current provides the measure of the radiation. Fig. 1. Picture of the SHAB with the spiral antenna taken with an optical microscope. The inset is a SEM picture showing a detail of free standing bridge structure of the microbolometer ISBN-14: 978-92-990073-2-7 1031