500 Mrad total-ionizing-dose tolerance of a holographic memory on an optical FPGA

Currently, radiation-hardened static random access memory (SRAM) based field programmable gate arrays (FPGAst are used frequently for space applications. Invariably, such SRAM-based FPGAs are used along with an electrically erasable programmable read-only memory (EEPROM). Although the radiation tolerance of data stored on EEPROMs is much higher than that stored on SRAMs, the radiation tolerance of the data on an EEPROM is not perfectly safe because electrons on the floating gates of transistors are also disturbed by strong radiation. If high-energy charged particles are incident to the EEPROM, then the EEPROM data might be destroyed by the radiation. In stark contrast, the radiation tolerances of holographic memories are perfect. Recording and reading of holographic memory can be executed optically. They never depend on electrons or holes. Moreover, data stored on holographic memory are read by summations of numerous light waves. The operation can be regarded as a majority voting operation. Therefore, even if half of a holographic memory is removed, the remaining half of the holographic memory can generate recorded data correctly. This paper describes a holographic memory based FPGA or an optically reconfigurable gate array (ORGA). Furthermore, this paper explains that a holographic memory can function correctly up to a 500 Mrad total-ionizing-dose, exhibiting 1,667 times higher radiation tolerance than current radiation-hardened VLSIs and FPGAs.