300 Mrad total-ionizing-dose tolerance of a holographic memory on an optically reconfigurable gate array

Currently, radiation-hardened field programmable gate arrays (FPGAs) are sought for embedded systems designed for use in space. However, in terms of soft-error and permanent failure, the radiation tolerances of configuration memories on current FPGAS are not high. Therefore, to remove the soft-error on configuration memories of FPGAS, optically reconfigurable gate arrays with a parallel configuration capability have been proposed. The optically reconfigurable gate array consists of an optically reconfigurable gate array VLSI, a holographic memory, and a laser array. Since the optically reconfigurable gate array allows high-speed scrubbing of its configuration memory, the soft-error factor on configuration memory can be removed from consideration. Moreover, the parallel configuration allows uses of radiation-damaged gate arrays so that the optically reconfig-urable gate array can increase the radiation tolerance. However to support such high-speed scrubbing, its optical part must work correctly even if it receives a large amount of radiation. This paper therefore presents a system in which the holographic memory can function correctly despite exposure up to 300 Mrad total-ionizing-dose, which is 300-times-higher radiation tolerance than those of current VLSIs and FPGAS.