The congruent Fe (0.03%wt):LiNbO3 crystals doped with different concentration of MgO (0, 2, 4, 6 mol%) were grown by Czochralski method in air atmosphere. The ultraviolet-visible absorption spectra, infrared absorption spectra of the crystals were measured in order to analyze their structure. The absorption edge of the Mg: Fe: LiNbO3 crystals shifted to the ultraviolet band compared with that of Fe: LiNbO3. The OH- absorption peaks of I and II crystals located at about 3483cm-1, while those of III and IV crystals shifted to 3536cm-1. The mechanism of OH- absorption peak shifting was studied. The light scattering ability resistance of Mg: Fe: LiNbO3 crystal was observed by straightly observing transmission facula distortion method. It indicated that light scattering ability resistance of III crystals was three orders of magnitude higher than that of Fe: LiNbO3 crystals. The exponential gain coefficient, diffraction efficiency and respond time of Mg: Fe: LiNbO3 crystals were measured by two-wave-coupling technology. The results indicate that exponential gain coefficient of Mg: Fe: LiNbO3 crystal was almost four times as that of iron-doped LiNbO3 and the response time exhibited four times shorter than that of iron-doped LiNbO3. Furthermore, the dynamic range was also calculated by the expression: M # = (τe ∠√η)/τω. The results indicated that Mg (4 mol%): Fe:LiNbO3 was the most proper holographic recording media material among four crystals in the paper.
The congruent Nd (Nd: 0. 2 wt %): LiNbO3 crystals doped with different concentration of MgO (MgO: 1, 3, 5,7mol %) have been grown by Czochralski method in air atmosphere. The crystals were made into samples after polarization, cut and polishing.
The infrared absorption spectra of Mg: Nd: LiNbO3 crystals were measured by using Fourier transform infrared spectrophotometer. The OH- absorption peaks of Mg (1mol %): Nd (0.2wt %): LiNbO3 crystal and Mg (3mol %): Nd (0.2wt %): LiNbO3 crystal located at about 3481cm-1, while that of Mg (5mol %): Nd (0.2wt %): LiNbO3 crystal and Mg (7mol %): Nd (0.2wt %): LiNbO3 crystal shifted to 3536cm-1. The mechanism of OH- absorption peak shifting was studied.
The resistance to photodamage of Mg: Nd: LiNbO3 crystals were measured by light spot distortion method. The results show that the photodamage threshold of Mg (5mol %) :Nd(0.2wt%):LiNbO3 was the highest(9.0×104W/cm2) among the samples. The mechanism of the photodamage resistance ability of Mg:Nd:LiNbO3 increasing was investigated.
Using a Q adjustable Nd: YAG laser as pumping light, the second harmonic generation (SHG) properties, including the phase matching temperature and SHG conversation efficiency of Mg: Nd: LiNbO3 were measured by 90 degree angle phase matching technology. The results showed that the SHG conversation efficiency of Mg (5mol %): Nd (0.2wt %): LiNbO3 was the highest (52%) among the samples at 96°C.
Ce:Fe:LiNbO3 crystal co-doped with CeO2 and Fe2O3 is grown by Czochralski method with Si-C bars as heaters. The exponential gain coefficient, diffraction efficiency and respond time of Ce:Fe:LiNbO3 crystal are measured by two-wave-coupling technology. The results indicate that the exponential gain coefficient of Ce:Fe:LiNbO3 is up to 22cm-1 and the diffraction efficiency is 78% and the photorefractive effect is better than that of Fe:LiNbO3 crystal. A thermal fixing experiment is carried on the Ce:Fe:LiNbO3 crystal, which conditions are that the crystal is heated to 120°C, the activated energy and the developing efficiency of Ce:Fe:LiNbO3 crystal are measured, and the decay time of a fixed grating is up to 110 years at the room temperature (20°C).
Ce:Cu:BSO crystal co-doped with CeO2 and CuO has been grown by the Czochralski method. The lattice constants, absorption spectrum, exponential gain coefficient, diffraction efficiency and respond time are measured. The lattice constants of Ce:Cu:BSO crystal are always larger than that of BSO crystal. Due to Ce and Cu ionic radii are larger than that of Bi3+ and Si4+, the lattice constants of doped crystal are larger than that of BSO crystal, thus make the absorption edge shift to the longer wavelength spectral range. The results indicate that the photorefraction of Ce:Cu:BSO crystal improves and the exponential gain coefficient and diffraction efficiency of Ce:Cu:BSO crystal improves two times compared with that of undoped BSO crystal. Furthermore, the photorefractive effect and the holographic storage effect of Ce:Cu:BSO crystal is better than that of undoped BSO crystal.
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