Operation of a Wideband Terahertz Superconducting Bolometer Responding to Quantum Cascade Laser Pulses |
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Authors: | S. Cibella M. Beck P. Carelli M. G. Castellano F. Chiarello J. Faist R. Leoni M. Ortolani L. Sabbatini G. Scalari G. Torrioli D. Turcinkova |
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Affiliation: | 1. Istituto di Fotonica e Nanotecnologie, CNR, Via Cineto Romano 42, 00156, Roma, Italy 2. Institute of Quantum Electronics, Eidgenossische Technische Hochschule Zurich, Zurich, Switzerland 3. Dipartimento di Ingegneria Elettrica e dell’Informazione, Università, Aquila, Italy 4. Dipartimento di Fisica, Università Roma TRE, Via della Vasca Navale 84, 00146, Roma, Italy
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Abstract: | We make use of a niobium film to produce a micrometric vacuum-bridge superconducting bolometer responding to THz frequency. The bolometer works anywhere in the temperature range 2–7?K, which can be easily reached in helium bath cryostats or closed-cycle cryocoolers. In this work the bolometer is mounted on a pulse tube refrigerator and operated to measure the equivalent noise power (NEP) and the response to fast (μs) terahertz pulses. The NEP above 100?Hz equals that measured in a liquid helium cryostat showing that potential drawbacks related to the use of a pulse tube refrigerator (like mechanical and thermal oscillations, electromagnetic interference, noise) are irrelevant. At low frequency, instead, the pulse tube expansion-compression cycles originate lines at 1?Hz and harmonics in the noise spectrum. The bolometer was illuminated with THz single pulses coming either from a Quantum Cascade Laser operating at liquid nitrogen temperature or from a frequency-multiplied electronic oscillator. The response of the bolometer to the single pulses show that the device can track signals with a rise time as fast as about 450?ns. |
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