We are developing monolithic arrays of corrugated feed horns fabricated in silicon for dual-polarization single-mode operation at 90, 145 and 220 GHz. The arrays consist of hundreds of platelet feed horns assembled from gold-coated stacks of micromachined silicon wafers. As a first step, Au-coated Si waveguides with a circular, corrugated cross section were fabricated; their attenuation was measured to be less than 0.15 dB/cm from 80 to 110 GHz at room temperature. To ease the manufacture of horn arrays, electrolytic deposition of Au on degenerate Si without a metal seed layer was demonstrated. An apparatus for measuring the radiation pattern, optical efficiency, and spectral band-pass of prototype horns is described. Feed horn arrays made of silicon may find use in measurements of the polarization anisotropy of the cosmic microwave background radiation.

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YBaCuO films by rf magnetron sputtering using single composite targets: Superconducting and structural properties Appl. Phys. Lett. 52, 1735 (1988); 10.1063/1.99716 RF sputter deposition of YBaCuO superconducting thin films from an oxide powder target AIP Conf.

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A high-Tc superconducting bolometer has been constructed using a YBa2Cu3Ox thin-film meander line 20 μm wide and 76 000 μm long, deposited on a SrTiO3 substrate. Radiation is absorbed by a thin film of Bi with well-characterized absorption properties deposited on a Si substrate in contact with the SrTiO3. At 1.8 Hz the measured bolometer response to a 500-K blackbody is 5.2 V/W (820 V/W extrapolated to dc), and the NEP is 5.7×10−8 W/(Hz)1/2 . The impact of apparent nonohmic behavior at the transition is discussed, as are ways of reducing the observed 1/f noise. The response time is 32 s and is dominated by the heat capacity of the SrTiO3 substrate.