Miniature Multilevel Optical Memristive Switch Using Phase Change Material

Optical memristive switches can be used as optical latching switches in which the switching state is changed only by applying an electrical Write/Erase pulse and maintained without an external power supply. We demonstrate an optical memristive switch based on a silicon multimode interferometer structure covered with nanoscale-sized Ge2Sb2Te5 (GST) material on top. The phase change of GST is triggered by resistive heating of the silicon layer beneath GST with an electrical pulse. Experimental results reveal that the optical transmissivity can be tuned in a controllable and repeatable manner. Partial crystallization of GST is obtained by controlling the width and amplitude of the electrical pulses. Crucially, we demonstrate that both Erase and Write operations, to and from any intermediate level, are possible with accurate control of the electrical pulses. Our work marks a significant step forward toward realizing photonic memristive switches without static power consumption, which are highly demanded in integrated photonics

Search for Scalar Leptons in e+e- collisions at \sqrt{s}=189 GeV

We report the result of a search for scalar leptons in e+e- collisions at 189 GeV centre-of-mass energy at LEP. No evidence for such particles is found in a data sample of 176 pb^{-1}. Improved upper limits are set on the production cross sections for these new particles. New exclusion contours in the parameter space of the Minimal Supersymmetric Standard Model are derived, as well as new lower limits on the masses of these supersymmetric particles. Under the assumptions of common gaugino and scalar masses at the GUT scale, we set an absolute lower limit on the mass of the lightest scalar electron of 65.5 Ge