We show that time-delayed nonlinear effects observed between exciton-polariton condensates can be used to create neural networks in which information is encoded in time. We form condensates on semiconductor microcavity using optical pulses that reach the sample at different times. Strongly nonlinear effects are induced by time-dependent interactions with a long-lived excitonic reservoir. Such nonlinearities make it possible to create a nonlinear XOR logic gate that performs operations with a picosecond time scale. A neural network based on such a logic gate performs a speech recognition tasks with high accuracy.
The concept of Neuromorphic Photonics introduces advantages of optical information processing into the neuromorphic engineering domain. Most of the current efforts in the field are focused on identifying the potential mechanisms for useful and flexible spiking neuron implementation. We propose a new approach in which microcavities exhibiting strong exciton-photon interaction may serve as building blocks of optical spiking neurons. Our experiments prove similarities between polariton in-out pulse characteristics and the fundamental spiking behavior of a biological neuron. These effects, evidenced in photoluminescence characteristics, arise within sub-ns timescales. The presented approach provides means for energy-efficient ultrafast processing of spike-like laser pulses.
Critical current and current-voltage characteristics of epitaxial Nb(Ti)N submicron ultrathin structures were measured as function of temperature. For 700-nm-wide bridge we found current-driven vortex de-pinning at low temperatures and thermally activated flux flow closer to the transition temperature, as the limiting factors for the critical current density. For 100-nm-wide meander we observed combination of phase-slip activation and vortex-anti-vortex pair (VAP) thermal excitation. Our Nb(Ti)N meander structure demonstrates high de-pairing critical current densities ~107 A/cm2 at low temperatures, but the critical currents are much smaller due to presence of the local constrictions.
In this paper, the design and technology of two types of 16-element photodiode arrays is described. The arrays were developed by the ITE and are to be used in detection of microdeflection of laser radiation at the Institute of Metrology and Biomedical Engineering in the Faculty of Mechatronics of Warsaw University of Technology.
The electrical and photoelectrical parameters of the arrays are presented.
In this paper a concept of a new bulk structure of p+-υ-n+ silicon photodiodes optimized for the detection of fast-changing radiation at the 1064 nm wavelength is presented. The design and technology for two types of quadrant photodiodes, the 8-segment photodiode and the 32-element linear photodiode array that were developed according to the concept are described.
Electric and photoelectric parameters of the photodiodes mentioned above are presented.
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