Non-volatile optoelectronic memory based on a non-periodic grating

Non-volatile optical memories represent a promising solution in data storage because of their high-speed, energy efficient, and durable data retention. Indeed, the interest of the research community in optical phase-change materials (O-PCMs) shows the urgent need for optical solutions in the non-volatile storage applications. Although several non-volatile optical memories using O-PCMs have been presented in the literature, their scalability is usually limited. In this article we show a non-volatile optoelectronic memory based on an electrically erasable programmable read-only grating (EEPROG) for the first time to our knowledge. A footprint per bit inversely proportional to the available bandwidth at the tunable source is demonstrated. Moreover, we show that to read the stored data in the EEPROG memory it is necessary only to sample the reflectivity spectrum of the EEPROG at a few wavelengths in a number equal to the number of bits stored in the memory. With 60 nm of available bandwidth at the tunable source (around 1500 nm), we demonstrate that one bit is stored in a footprint of 9.1 μm ×4.2 μm of the EEPROG memory. Higher available bandwidths would reduce the footprint per bit. The advantage with respect to the state of the art is the scalability of this memory, which represents one of the major bottlenecks of optical non-volatile memories. Indeed, the presented device allows a sequence of bits to be stored sequentially along the same waveguided structure, thus introducing a new level of scalability for optical non-volatile memories. The waveguiding device includes a Si 3 N 4 wire and a thin layer of Sb 2 S 3 as PCM, enabling non-volatile operations. The approach presented for storing and reading data is completely novel and could pave the way for a new series of non-volatile memories useful in several fields, including neuromorphic neural networks.