Energy-Efficient Photonic Memory Cell with Spatially Separated Recording/Erasing and Readout Channels

Phase-change material Ge2Sb2Te5 (GST) is a promising candidate for nonvolatile photonic devices due to its phase stability, different absorption coefficients in the amorphous and crystalline phase, and relatively fast response. Here, an energy-efficient design of a photonic nonvolatile memory that stores its logical status as GST phase states is proposed. The device is based on the silicon-on-insulator (SOI) substrate and consists of the fourfold symmetric strip waveguide crossing incorporated with the square GST patch and a multimode interference (MMI) loop reflector. The distinctive feature of the proposed cell is two spatially separated recording/erasing and readout channels. One of the crossed waveguides is connected to the MMI loop reflector and used for recording/erasing. The other waveguide is used for readout. The numerical simulation of the light transmission through the device in question shows that the MMI loop reflector provides 45% and 80% higher absorption values in comparison with waveguide end reflector and straightforward transmission, respectively. This fact allows the more efficient utilization of the guided mode energy and makes the proposed photonic memory cell an attractive node element for photonic integrated circuits.