Silicon photonic read-only memory

In this paper, a CMOS-compatible in-plane micrometer-size optically readable nonvolatile-memory device is proposed and analyzed. It consists of an electrically erasable programmable read-only memory (EEPROM) integrated on a high-index-contrast silicon-on-insulator (SOI) rib waveguide. Our calculations indicate that variations on the order of 10^-4 of the waveguide effective refractive index can be achieved for the typical values of stored charge (on the order of 10¹² q_e/cm²) on a floating gate. A microring resonator, based on such waveguide, efficiently converts the calculated index variations into strong intensity variations. This photonic structure can be used to create nonvolatile optically readable memory states in a photonic device [photonic EEPROM (PEEPROM)] with an ultrafast read time. A microring-resonator intensity-modulator PEEPROM is predicted to exhibit a modulation depth of 91% (10.4 dB) between the uncharged and charged (3.75×10¹² q_e/cm²) states. The read time of the device is only 9 ps, which is at least two orders of magnitude shorter than that of a standard two-transistor electrically readable EEPROM.