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Ultralow-power all-optical RAM based on nanocavities


Optical random-access memory (o-RAM) has been regarded as one of the most difficult challenges in terms of replacing its various functionalities in electronic circuitry with their photonic counterparts. Nevertheless, it constitutes a key device in optical routing and processing. Here, we demonstrate that photonic crystal nanocavities with an ultrasmall buried heterostructure design can solve most of the problems encountered in previous o-RAMs. By taking advantage of the strong confinement of photons and carriers and allowing heat to escape efficiently, we have realized all-optical RAMs with a power consumption of only 30 nW, which is more than 300 times lower than the previous record, and have achieved continuous operation. We have also demonstrated their feasibility in multibit integration. This paves the way for constructing a low-power large-scale o-RAM system that can handle high-bit-rate optical signals.

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Figure 1: Device structure and static response.
Figure 2: Dynamic one-bit RAM operation.
Figure 3: RAM operation for different bias powers.
Figure 4: Integrated o-RAM operation for a four-bit signal train.


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This work was supported by the National Institute of Information and Communications Technology (NICT). The authors thank T. Tamamura, E. Kuramochi, H. Onji and Y. Shouji for support in fabricating the device, and K. Kitayama, T. Enoki, Y. Hibino, K. Kato, I. Yokohama and Y. Tokura for their continuous encouragement.

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Authors and Affiliations



K.N. performed the experiment, analysed the data and wrote the manuscript. A.S. supported the o-RAM design and measurement. S.M., T.S. and Y.K. fabricated the o-RAM samples. Y.S., T.S. and R.T. helped with the demonstration set-up for the parallel o-RAM system. M.N. wrote part of the manuscript and led the project.

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Correspondence to Kengo Nozaki or Masaya Notomi.

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The authors declare no competing financial interests.

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Nozaki, K., Shinya, A., Matsuo, S. et al. Ultralow-power all-optical RAM based on nanocavities. Nature Photon 6, 248–252 (2012).

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