Abstract
The electrochemical metallization (ECM) mechanism is emerging as a promising approach for the development of optical memristors-nonvolatile memory systems proposed for use as artificial synapses in neuromorphic computing applications. ECM memristors offer exceptional operating dynamics and power efficiency compared to other systems, but challenges with reproducible cycle-to-cycle state switching and the absence of advanced optical functionalities hinder their integration into photonic systems. In this work, an ECM free-standing memristor structure is proposed, which simultaneously offers wavelength-dependent multilevel nonvolatile optical storage, volatile light modulation, and dynamic polarization control. It is demonstrated that in the presence of a resonance, the optical readout provides noise-free, robust, and significantly more accurate information about the memristor's state than electrical measurement. The use of light allows to gain insight into the intermediate electrical levels of the device as it transitions between high and low resistance states and to recover the complete record of applied voltages even when stochastic filament ruptures occur. Finally, the investigations show that spectroscopic ellipsometry provides real-time information on the dynamics of cation movement and the corresponding permittivity changes at the interfaces between the switching layer and the electrodes, thus becoming a complementary characterization method for ECM memristors alongside state-of-the-art techniques.