Holographic recording in a doubly doped Lithium Niobate crystalwith two wavelengths; a blue laser diode and a green laser

摘要

A doubly-doped LiNbO_3 (LN) crystal has been well used as a nonvolatile two-wavelength recording material. By using two levels of the crystal, two-kind holograms can be recorded on one crystal; a hologram is recorded with a 405–nm blue laser diode (LD) for a deep Mn level, and another hologram is with a 532-nm green laser for a shallow Fe level. The recording capacity doubles. A 780–nm LD is non-volatile reconstructing source since the LD line is insensitive to both levels. Multiplexed reconstructed images are demonstrated by using a sharp angular selectivity of a volume LN crystal keeping Bragg condition with spherical reconstructions.