Neuromorphic computing system inspired by the human brain has the capability of breaking through the von Neumann bottleneck, which can improve the efficiency of data processing. To deploy efficient neuromorphic systems, the development of synaptic devices is imperative. However, achieving tunable synaptic behaviors in a single transistor remains challenging. In this work, a silicon nanowire-based photoelectronic synaptic transistor is developed to achieve tunable synaptic behaviors. Using the floating-body effect and a cylindrical surrounding double-gate (CSDG) structure, we simulated excitatory and inhibitory synaptic plasticity in a single device. Additionally, our device also simulated various synaptic characteristics by modulating the bias voltages and light pulses, such as excitatory and inhibitory postsynaptic current (PSC), short-term potentiation (STP), short-term depression (STD), long-term potentiation (LTP), and forgetting behavior. This study provides an effective strategy for developing tunable photoelectronic synapses. Furthermore, Si processing compatibility also makes the synaptic device a promising contender for the implementation of neuromorphic computing.
The output characteristics of distributed feedback (DFB) lasers are greatly affected by different values of the parameters in rate equations. However, there is a lack of simple and feasible parameter extraction methods to determine the values of these parameters. In this paper, a straightforward method for modeling and parameter extraction of the equivalent circuit model for DFB laser based on rate equations is presented which mainly combines those intrinsic parameters into new parameters that can be easily extracted from the external performance of the laser. Before extraction, a laser equivalent circuit model is established based on the transformed rate equation, which can accurately simulate the nonlinear characteristics of DFB lasers. Moreover, based on the output characteristics of semiconductor lasers, the parameters of them are extracted by formula transformation and data fitting. The extracted parameter values are comparable to the reported theoretical and experimental data, validating the accuracy of the extraction method in this paper. Additionally, good agreement is reached between the simulation results and the reference data when the extracted parameter values are used in the model. Meanwhile, it turns out that changes in different physically plausible parameter values have different effects on the external output characteristics. In summary, the method of parameter extraction described in this paper has a good guiding significance for the improvement of laser manufacturing and performance.
A variable weight two-dimensional Multi-Diagonal (VW 2D-MD) code is proposed for supporting the Quality of Service (QoS) differentiation in the spectra/spatial Optical Code Division Multiple Access (OCDMA) system. The proposed two-dimensional code is constructed by utilizing the regular one-dimensional Multi-Diagonal (1D-MD) code for spatial coding and the new proposed variable weight MD code as the spectral code. Due to the property of zero cross-correlation, the multiple-access interference (MAI) can be fully eliminated, and the phase induced intensity noise (PIIN) can also be suppressed. In addition, the proposed 2D code can accommodate more active users compared to the 1D VW zero crosscorrelation (ZCC) code. Finally, the simulation setup with the proposed code shows that the performance of the user with larger code weight is better than that of the user with smaller code weight.
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