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The integration of the transparent ITO/NiO/ITO Resistive Random-Access Memory (ReRAM) with vertically-coupled bus waveguides, which is ultimately emerged as a ReRAM-based microdisk resonator fabricated on lithium niobate (LiNbO3) substrate, is successfully realized. The transparent ITO and NiO layers are deposited by radio-frequency sputtering technique, while the bus waveguides in LiNbO3 is achieved by a proton-exchange method. The ReRAM-based microdisk resonator thus designed and fabricated have dual functionality of memory and optical spectral filtering capabilities. When the ReRAM microdisk resonator is electronically set at different memory states, that is, ReRAM is alternatively set in high-resistance state (HRS) and low-resistance state (LRS), the corresponding spectral shifts detected at both through and drop ports are noticeable different, when compared with those obtained before and after subjecting the ReRAM to a required forming process. Specifically, the spectral shift associated with the LRS state of ReRAM between the through and drop port terminal is around 4.4 nm, as compared to the spectral shift of approximately 1.7 nm that is associated with the HRS state of ReRAM between the same two terminals. The aforementioned characteristics of selective light wave filtering can be selectively tuned by varying the ReRAM device dimensions. The adoption of the different thin-film materials for the ReRAM fabrication may also play an important role in spectral tuning. Most important of all, because of different spectral shifts observed, the particular memory state of ReRAM could possibly and uniquely be interrogated by an optical means. The resultant discovery opens a new pathway in the future to the realization of one of the new optical memory devices.
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