| 摘要 |
New methods are presented for multiplexing volume holograms in electrooptic materials. Multiple volume holograms can be superimposed in a medium and be individually addressed by tuning the underlying refractive index of the medium or the crystal parameters, while keeping the external parameters (wavelength, angles) fixed. According to the presented methods, the refractive index and crystal parameters of the material can be varied via the electrooptic, elastooptic or piezoelectric effects, alone or in combination with each other, by tuning the value of an applied electric field, or by tuning an applied mechanical stress, or by changing the material temperature. Volume holograms that have been multiplexed by either wavelength or angle or electric field or mechanical stress or temperature can be individually addressed by any one of the same five parameters. Additionally, selective, updatable fixing and erasing of volume holograms in photorefractive media is described. Each holographic page may be fixed individually and overwritten without destroying the other fixed pages. Further, Second Harmonic Generation and Parametric Amplification by optically induced periodic poling in ferroelectric photorefractive materials is described.
|
