Agility of vortex-based nanocontact spin torque oscillators

We study the agility of current-tunable oscillators based on a magnetic vortex orbiting around a point contact in spin-valves. Theory predicts frequency-tuning by currents occurs at constant orbital radius, so an exceptional agility is anticipated. To test this, we have inserted an oscillator in a microwave interferometer to apply abrupt current variations while time resolving its emission. Using frequency shift keying, we show that the oscillator can switch between two stabilized frequencies differing by 25% in less than ten periods. With a wide frequency tunability and a good agility, such oscillators possess desirable figures of merit for modulation-based rf applications.Comment: 3 pages, 3 figure

Ultra-low-threshold continuous-wave and pulsed lasing in tensile-strained GeSn alloys

Strained GeSn alloys are promising for realizing light emitters based entirely on group IV elements. Here, we report GeSn microdisk lasers encapsulated with a SiNx stressor layer to produce tensile strain. A 300 nm-thick GeSn layer with 5.4 at% Sn, which is an indirect-bandgap semiconductor as-grown, is transformed via tensile strain engineering into a direct-bandgap semiconductor that supports lasing. In this approach, the low Sn concentration enables improved defect engineering and the tensile strain delivers a low density of states at the valence band edge, which is the light hole band. We observe ultra-low-threshold continuous-wave and pulsed lasing at temperatures up to 70 K and 100 K, respectively. Lasers operating at a wavelength of 2.5 μm have thresholds of 0.8 kW cm−2 for nanosecond pulsed optical excitation and 1.1 kW cm−2 under continuous-wave optical excitation. The results offer a path towards monolithically integrated group IV laser sources on a Si photonics platform

Modélisation 3D des équations de Maxwell et de Boltzmann : rôle du guide d’onde sur la réponse d’un photo-commutateur

International audienc

Modélisation 3D des équations de Maxwell et de Boltzmann : rôle du guide d’onde sur la réponse d’un photo-commutateur

International audienc

Modélisation 3D des équations de Maxwell et de Boltzmann : rôle du guide d’onde sur la réponse d’un photo-commutateur

International audienc

Modélisation 3D des équations de Maxwell et de Boltzmann : rôle du guide d’onde sur la réponse d’un photo-commutateur

International audienc

Invited PaperTemperature dependence of SiGe HBT static and dynamic characteristics

The SiGe HBT is a good candidate for MIC, MMIC and high speed logic circuits below 50GHz at ambient temperature and also at cryogenic temperature. A static and dynamic analysis of abrupt junction SiGe HBTs is presented in a wide range of temperatures, biases and frequencies up to 50GHz. The different transit times are investigated by analyzing the temperature dependence of the devices'static and HF properties between 50K and 300K

Mesure de la permittivité du a-Si:H entre 0.5 et 3 THz

International audienc