Simplified architectures with homodyne detection for high capacity Lippmann data storage

Lippmann storage systems are close to holographic memories: binary data are encoded as pixels on an image beam by means of a spatial light modulator. This data page is imaged into the plane of a mirror set beneath the recording medium. Conversely to holography, the image beam interferes with its reflection onto this mirror, and not with an external reference beam [1-3]. These interferences record a grating in the sensitive material. The absence of any reference simplifies the architecture at the expense on stringent requirements on the set-up [4]. The advantages of the Lippmann systems justify these constraints. Several pages are successively recorded, each at a specific wavelength. The readout is performed with a plane wave at the wavelength used for recording. In conventional Lippmann systems, the mirror is removed during readout, and only the diffracted intensity is detected. On the contrary, we propose to let the mirror in place. During readout, the diffracted amplitude thus interferes with the plane wave corresponding to the readout wave reflected onto the mirror. This homodyne scheme and some of its variants were discussed for bit-oriented memories previously [5,6]. We present this homodyne detection for page-oriented Lippmann systems.