Abstract: Device for memory-storage of a coherent image in a multimode optical cavity. A coherent light source generates a signal wave and a reference wave and provides these waves to optical guiding devices. These optical guiding devices form a closed loop in which the signal wave circulates. The guiding devices form a multimode optical cavity having a Fourier plane. An amplifying interactive medium is disposed within the cavity on the path of the signal wave and at the Fourier plane. Within the interactive medium, the signal wave interferes with the reference wave in order to create a diffraction grating. Each signal wave thus receives energy from the reference wave with which it interferes. A semi-transparent beam splitter is disposed within the cavity on the path of the signal wave in order to extract a portion of the energy from the optical cavity.