6 research outputs found
Nano-optical observation of cascade switching in a parallel superconducting nanowire single photon detector
The device physics of parallel-wire superconducting nanowire single photon
detectors is based on a cascade process. Using nano-optical techniques and a
parallel wire device with spatially-separate pixels we explicitly demonstrate
the single- and multi-photon triggering regimes. We develop a model for
describing efficiency of a detector operating in the arm-trigger regime. We
investigate the timing response of the detector when illuminating a single
pixel and two pixels. We see a change in the active area of the detector
between the two regimes and find the two-pixel trigger regime to have a faster
timing response than the one-pixel regime.Comment: 11 pages, 2 figure
Electrical characterisation of higher order spin wave modes in vortex-based magnetic tunnel junctions
International audienceAbstract NiFe-based vortex spin-torque nano-oscillators (STNO) have been shown to be rich dynamic systems which can operate as efficient frequency generators and detectors, but with a limitation in frequency determined by the gyrotropic frequency, typically sub-GHz. In this report, we present a detailed analysis of the nature of the higher order spin wave modes which exist in the Super High Frequency range (3–30 GHz). This is achieved via micromagnetic simulations and electrical characterisation in magnetic tunnel junctions, both directly via the spin-diode effect and indirectly via the measurement of the coupling with the gyrotropic critical current. The excitation mechanism and spatial profile of the modes are shown to have a complex dependence on the vortex core position. Additionally, the inter-mode coupling between the fundamental gyrotropic mode and the higher order modes is shown to reduce or enhance the effective damping depending upon the sense of propagation of the confined spin wave