Large-scale integration of wavelength-addressable all-optical memories on a photonic crystal chip


Photonic integration has long been pursued, but remains immature compared with electronics. Nanophotonics is expected to change this situation. However, despite the recent success of nanophotonic devices, there has been no demonstration of large-scale integration. Here, we describe the large-scale and dense integration of optical memories in a photonic crystal chip. To achieve this, we introduce a wavelength-addressable serial integration scheme using a simple cavity-optimization rule. We fully exploit the wavelength-division-multiplexing capability, which is the most important advantage of photonics over electronics, and achieve an extremely large wavelength-channel density. This is the first demonstration of the large-scale photonic integration of nanophotonic devices coupled to waveguides in a single chip, and also the first dense wavelength-division-multiplexing nanophotonic devices other than filters. This work paves the way for optical random-access memories and for a large-scale wavelength-division-multiplexing photonic network-on-chip.

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Figure 1: Designs of integrated multi-bit optical memory (o-RAM) arrays.
Figure 2: Modified Lx ( ≈ 2–5) nanocavity design and characteristics.
Figure 3: Thirty-two cascaded integrated InGaAsP/InP BH nanocavities and their bistable operation.
Figure 4: Demonstration of 28-bit write/readout bit-memory operation in an InGaAsP/InP BH nanocavity array.
Figure 5: Cascaded integrated 128-Si-nanocavity array.
Figure 6: Bistable 105-bit memory operation of integrated Si nanocavities.


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The authors thank T. Tamamura, H. Onji, S. Fujiura and Y. Shouji for their support in fabricating the device, H. Onji and S. Fujiura for their support in measuring the devices, and T. Sogawa and Y. Tokura for their continuous encouragement.

Author information




M.N. planned the project. E.K., A.S., K.N. and M.N. designed the device. E.K. designed the cavity and performed the numerical simulations. E.K. and K.T. prepared the pattern data. E.K. and H.S. fabricated the Si samples. K.T., T.S., S.M. and E.K. fabricated the InP-based samples. K.N. and E.K. performed measurements. E.K. and M.N. wrote the manuscript.

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Correspondence to Eiichi Kuramochi or Masaya Notomi.

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The authors declare no competing financial interests.

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Kuramochi, E., Nozaki, K., Shinya, A. et al. Large-scale integration of wavelength-addressable all-optical memories on a photonic crystal chip. Nature Photon 8, 474–481 (2014).

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