Abstract
Artificial intelligence takes inspiration from the functionalities and structure of the brain to solve complex tasks and allow learning. Yet, hardware realization that simulates the synaptic activities realized with electrical devices still lags behind computer software implementation, which has improved significantly during the past decade. Herein, the capability to emulate synaptic functionalities by exploiting surface plasmon polaritons (SPPs) is shown. By depositing photochromic switching molecules (diarylethene) on a thin film of gold, it is possible to reliably control the electronic configuration of the molecules upon illumination cycles with UV and visible light. These reversible changes modulate the dielectric function of the photochromic film and thus enable the effective control of the SPP dispersion relation at the molecule/gold interface. The plasmonic device displays fundamental functions of a synapse such as potentiation, depression, and long‐term plasticity. The integration of such plasmonic devices in an artificial neural network is deployed in plasmonic neuroinspired circuits for optical computing and data transmission.
Highlights
Artificial intelligence takes inspiration from the functionalities and structure of ered the basis of learning processes and the brain to solve complex tasks and allow learning
The experiments are all conducted at room temperature and use total internal reflection (TIR) in Kretschmann configuration, this being an efficient method for surface plasmon polaritons (SPPs) excitation for vertical material stacks.[17,18]
The optical excitation of SPPs in the plasmonic synaptic device is shown in Figure 1b
Summary
The experiments are all conducted at room temperature and use total internal reflection (TIR) in Kretschmann configuration, this being an efficient method for SPP excitation for vertical material stacks.[17,18] The optical excitation of SPPs in the plasmonic synaptic device is shown in Figure 1b (a detailed schematic of the setup is shown in Figure S1, Supporting Information). Upon illumination with UV light, the colorless open isomer undergoes a photochemically induced ring-closure reaction to the fully conjugated closed isomer. The occurrence of this is valence bond tautomerization that is indicated by the broad absorption peak. By illumination with visible light, the closed isomer undergoes the reverse ring-opening reaction and thereby reversibly switches back to the initial open isomer.[21,22,23] Lightemitting diodes of 315 and 565 nm wavelength (with irradiance of 10À6 μW mmÀ2) were used for this. As a result of the change in optical gap of the DAE between the open and closed form, the dielectric function εd of the DAE film is modulated
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