Abstract: Normal operation of complementary metal-oxide semiconductor (CMOS) devices entails the emission of picosecond pulses of light, which can be used to diagnose circuit problems. The pulses that are observed from submicron sized field effect transistors (FETs) are synchronous with logic state switching. Picosecond Imaging Circuit Analysis (PICA), a new optical imaging technique combining imaging with timing, spatially resolves individual devices at the 0.5 micron level and switching events on a 10 picosecond timescale. PICA is used here for the diagnostics of failures on two VLSI microprocessors.

Abstract: We present a compact packaging technique for coupling light from a single-mode telecommunication fiber to cryogenic single-photon sensitive devices. Our single-photon detectors are superconducting transition-edge sensors (TESs) with a collection area only a factor of a few larger than the area of the fiber core which presents significant challenges to low-loss fiber-to-detector coupling. The coupling method presented here has low loss, cryogenic compatibility, easy and reproducible assembly and low component cost. The system efficiency of the packaged single-photon counting detectors is verified by the “triplet method” of power-source calibration along with the “multiple attenuator” method that produces a calibrated single-photon flux. These calibration techniques, when used in combination with through-wafer imaging and fiber back-reflection measurements, give us confidence that we have achieved coupling losses below 1 % for all devices packaged according to the self-alignment method presented in this paper.