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Cold-Electron Bolometer Arrays for THz Detection
Leonid S. Kuzmin
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, Mikhail A. Tarasovc,d, , Sumedh H. Mahashabdea, and Valerian S.Edelmane, Chalmers University of Technology, Gothenburg, Sweden Moscow State University, Russia, c Niznij Novgorod State Technical University, Russia d V.Kotel'nikov Institute of Radio Engineering and Electronics, Moscow, Russia c P.Kapitza Institute for Physical Problems, Moscow, Russia
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a,b,c

Abstract-- Various concepts of Cold-Electron Bolometer (CEB) Arrays are considered for THz detection from 300 GHz to 7 THz. A series array of 64 cold electron bolometers designed for 7 THz operation was fabricated and dc tested at temperatures down to 50 mK. At 277 mK temperature sensitivity is 50 µV/mK. Optical response to THz radiation is 300 µV for 2.7/0.3 K temperature difference. Noise of such array is 26 nV/Hz1/2. Response of more than 2 mV was measured for 5 K blackbody temperature in array designed for 350 GHz

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I. I

NTRODUCTION

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BACKGR

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Thermal response, V/mK

E develop cold electron bolometers for use in the SAFARI detector for the SPICA (SPace Infrared telescope for Cosmology Astrophysics) space borne 3.5 m diameter telescope. The SAFARI (SpicA FAR-infrared Instrument) instrument 34-210 µm wave band is divided into several channels. Our design is intended for 7 THz channel with spectral range 34-60 µm (5-9 THz). The goal is to obtain the noise equivalent power down to NEP=10-19 W/Hz1/2 for power load P0=20 aW at operating base temperature 50 mK. Another application of such array could be a detector in cryogenic Fourier Transform Spectrometer (FTS) in THz frequency band. Image of the sample is presented in Fig. 1. In the center of chip there are placed 4 arrays each consisting of 64 bolometers. Diagonal pairs of arrays are receiving orthogonal polarizations. Each bolometer is connected to a dipole antenna designed for 7 THz central frequency.

Figure 1. SEM image of the sample with four arrays each consisting of 64 bolometers.

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Optical response,V

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II. RESULTS Samples were dc tested in dilution refrigerator at temperatures down to 50 mK. For sensitivity measurements chip with such sample was placed on the flat side of extended hyper-hemisphere Si lens and optically tested using a blackbody radiation source. At base temperature of 277 mK we measured temperature sensitivity and response to hot/cold load (Fig. 2). Temperature response is consistent to our previous measurements both with single bolometers and arrays consisting of 10 bolometers. Obtained optical response for 7 THz 2.7 K blackbody radiation is 100 µV/K. Such structure also receives radiation at multiple wavelengths up to x8, which means that we also measuring response at some frequencies below 7 THz. Similar array scaled for 350 GHz frequency band demonstrated optical response up to 2 mV for 5K blackbody temperature.

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Voltage, mV

Figure 2. Voltage response of array to small temperature change at 277 mK and voltage response to hot/cold load with temperature difference 3 K. REFERENCES
[1] Kuzmin, L. 2D Array of Cold-Electron Bolometers for Ultrasensitive Polarization Measurements. Radiophisika. . LIV, N89, 607 (2011); Radiophysics and Quantum Electronics (2012). [2] Kuzmin, L. "Distributed Antenna-Coupled Cold-Electron Bolometers for Focal Plane Antenna", Proc. ISSTT conference, pp 154-158 (2008).