1 Ultrafast Superconducting Bolometer Receivers for Terahertz Applications R. V. Ozhegov 1, 2 , A. V. Smirnov 1 , Yu. B. Vakhtomin 1, 2 , K. V. Smirnov 1, 2 , A. V. Divochiy 1, 2 , and G. N. Goltsman 1 1 Moscow State Pedagogical University, 29 Malaya Pirogovskaya St., Moscow 119992, Russia 2 SCONTEL, 5/22 Rossolimo St., Moscow 119021, Russia Abstract— The research by the group of Moscow State Pedagogical University into the hot- electron phenomena in thin superconducting films has led to the development of new types of detectors [1, 2] and their use both in fundamental and applied studies [3–6]. In this paper, we present the results of testing the terahertz HEB receiver systems based on ultrathin (∼ 4 nm) NbN and MoRe detectors with a response time of 50ps and 1ns, respectively. We have developed three types of devices which differ in the way a terahertz signal is coupled to the detector and cover the following ranges: 0.3–3 THz, 0.1–30 THz and 25–70 THz. The main characteristics of the receiver systems are presented in Table 1. Table 1. Type of detector 1/1a 2/2a 3/3a Frequency range, THz 0.3–3 25–70 0.1–30 NEP, W · Hz -0.5 5–7 · 10 -14 /3–5 · 10 -13 1–2 · 10 -12 /4–5 · 10 -12 4–6 · 10 -11 /1–2 · 10 -10 Response time, ns 1/0.05 1/0.05 1/0.05 Dynamic range, μW 1 50 10 5 In the case of the receiving system optimized for 0.3–3 THz, the sensitive element (a strip of a superconductor with planar dimensions of 0.2 μm (length) by 1.7 μm (width)) was integrated with a planar broadband log-spiral antenna (detector type 1/1a in Table 1). For additional focusing of the incident radiation a silicon hyperhemispherical lens was used. For the 0.1–30THz receiving system (detector type 3/3a in Table 1), the sensitive element was patterned as parallel strips (2 μm wide each) filling an area of 500 × 500 μm 2 with a filling factor of 0.5. In the receiving system of this type we used direct coupling of the incident radiation to the sensitive element. In the 25–70 THz range (detector type 2/2a in Table 1) we used a square-shaped superconducting detector with planar dimensions of 10 × 10 μm 2 . Incident radiation was coupled to the detector with the use of a germanium hyperhemispherical lens. The response time of the above receiving systems is determined by the cooling rate of the hot electrons in the film. That depends on the electron-phonon interaction time, which is less for ultrathin NbN than in MoRe. REFERENCES 1. Divochiy, A., F. Marsili, D. Bitauld, etal., Nature Photonics, Vol. 2, 302–306, 2008. 2. Finkel, M. I., S. N. Maslennikov, and G. N. Gol’tsman, “Terahertz heterodyne receivers based on superconductive hot-electron bolometer mixers,” Radiophysics and Quantum Electronics, Vol. 48, No. 10–11, 859–864, 2005. 3. Hostein, R., A. Michon, G. Beaudoin, et al., Appl. Phys. Lett., Vol. 93, 073106, 2008. 4. Takesue, H., S. Nam, Q. Zhang, etal., Nature Photonics, Vol. 1, 343–348, 2007. 5. Planken, P., Nature, Vol. 456, 454–455, 2008. 6. Huber, A. J., F. Keilmann, J. Wittborn, et al., Nano Lett., Vol. 8, No. 11, 3766–3770, 2008.