42 research outputs found
Feasibility of conductive embroidered threads for I2C sensors in microcontroller-based wearable electronics
In recent years, the importance of flexible and textile electronics in the field of wearable devices has continuously increased, as they are expected to replace conventional wires that exhibit limited resistance to the mechanical stress occurring in on-body applications. Wearable health devices (WHDs) can provide physiological information about various body parts and employ distributed sensor networks. Among the sensors typically integrated within WHDs, those based on the I2C communication protocol are very common and exploit signals transmitted at frequencies up to hundreds of kilohertz. Therefore, robust communication is required to guarantee a proper transmission of the signal at those frequencies. In this context, we have realized embroidered conductive threads exhibiting a lower resistance, appositely designed to replace conventional wires in a microcontroller-based wearable device employing I2C sensors. A commercial conductive thread (silver coated polyamide) was used to embroider the conductive lines on to cotton fabric. Preliminary measurements were performed to characterize the response of these materials to signals typically operated within the I2C communication protocol at different path lengths. Resistive measurements have also been performed to stimulate different environmental conditions, that is, temperature, the effect of sweating, and repeated washing cycles, also apply mechanical stress, i.e. twisting, with promising results that validate our conductive paths for digital signal communication
Single-photon detection and cryogenic reconfigurability in Lithium Niobate nanophotonic circuits
Lithium-Niobate-On-Insulator (LNOI) is emerging as a promising platform for
integrated quantum photonic technologies because of its high second-order
nonlinearity and compact waveguide footprint. Importantly, LNOI allows for
creating electro-optically reconfigurable circuits, which can be efficiently
operated at cryogenic temperature. Their integration with superconducting
nanowire single-photon detectors (SNSPDs) paves the way for realizing scalable
photonic devices for active manipulation and detection of quantum states of
light. Here we report the first demonstration of these two key components
integrated in a low loss (0.2 dB/cm) LNOI waveguide network. As an experimental
showcase of our technology, we demonstrate the combined operation of an
electrically tunable Mach-Zehnder interferometer and two waveguide-integrated
SNSPDs at its outputs. We show static reconfigurability of our system with a
bias-drift-free operation over a time of 12 hours, as well as high-speed
modulation at a frequency up to 1 GHz. Our results provide blueprints for
implementing complex quantum photonic devices on the LNOI platform
Hot-spot relaxation time current dependence in niobium nitride waveguide-integrated superconducting nanowire single-photon detectors
We investigate how the bias current affects the hot-spot relaxation dynamics in niobium nitride. We use for this purpose a near-infrared pump-probe technique on a waveguide-integrated superconducting nanowire single-photon detector driven in the twophoton regime. We observe a strong increase in the picosecond relaxation time for higher bias currents. A minimum relaxation time of (22 ± 1) ps is obtained when applying a bias current of 50% of the switching current at 1.7 K bath temperature. We also propose a practical approach to accurately estimate the photon detection regimes based on the reconstruction of the measured detector tomography at different bias currents and for different illumination conditions