Fixable complementary gratings in photorefractive BaTiO(3)

Dielectrically induced sensitivity enhancements in electro-optic field sensors

The sensitivity of an electro-optic (EO) field sensor depends inversely on the dielectric constant of the nonlinear crystal. In EO sensors based on lithium niobate the effective value of this dielectric constant is affected by dielectric relaxation effects and is identified with its smaller, high-frequency component. Because of this effect, the EO modulation is significantly enhanced, thus improving the field strength sensitivity.

Fixed three-dimensional holographic images

Three-dimensional holograms were recorded in a cerium-doped, strontium barium niobate (SBN:75) photorefractive crystal. These holograms are shown to not degrade after more than one week of continuous readout and to reconstruct reproductions of the original object with an observable field of view of approximately 35 degrees.

Thermal fixing of holographic gratings in BaTiO(3)

Fixing of a holographic grating in a single BaTiO(3) crystal is studied in detail by means of a thermal process. Above T = 78 °C, oscillations of the diffracted intensity of the sample appear, which are related to the fixing process. Different methods to perform and optimize the fixing process are described. A fixed diffraction efficiency of ~25% was obtained. Self-enhanced as well as self-depleted diffraction from the fixed photorefractive gratings was observed.

Noise-free holographic storage in iron-doped lithium niobate crystals

We show that fanning noise in lithium niobate crystals can have a deleterious effect on holographic storage in configurations in which the c axis and the grating wave vector coincide, for both ordinary and extraordinary light polarizations. We then demonstrate that this noise is drastically reduced when the c axis is perpendicular to the grating wave vector. Images have been fixed and read out for many hours at high intensity levels, demonstrating long-term storage and good-quality image recall.

Electrical fixing of photorefractive holograms in Sr(0.75) Ba(0.25)Nb(2)O(6)

Photorefractive holograms stored in Sr(0.75)Ba(0.25)Nb(2)O(6) crystals are electrically fixed at room temperature. The fixed holograms can be read out directly or after a positive-voltage pulse is applied that can dramatically enhance the diffraction efficiency. Single gratings as well as images are recorded and fixed.