An investigation of the specially doped cerium:iron:lithium niobate photorefractive crystals: Optical properties and applications.

摘要

The first half of this dissertation presents investigations of the material aspects of photorefractive properties of LiNbO{dollar}sb3{dollar} doped with cerium (Ce) and iron (Fe). A two-wave coupling approach is utilized to measure the photorefractive sensitivity, response time, and material dynamic range. The wavelength-sensitivity range of the crystal is determined by using the optical absorption method. The absorption spectra show that the Ce:Fe:LiNbO{dollar}sb3{dollar} crystal has a higher photorefractive sensitivity in the red light region than singly doped and undoped LiNbO{dollar}sb3{dollar} crystals. These characterization measurements show that the Ce:Fe:LiNbO{dollar}sb3{dollar} crystal has the overall best photorefractive properties which make it very suitable for practical applications for photonic technologies. Both theoretical and experimental results show strong temperature dependence of the light-induced scattering noise due to thermally activated ionic charges. Based on this result, a method for signal-to-noise ratio (SNR) enhancement is proposed. It is shown that the scattering noise can be effective reduced if the crystal is operated at an elevated temperature.; The remaining of this dissertation is concerned with the applications of the Ce:Fe:LiNbO{dollar}sb3{dollar} photorefractive crystal. First, an optical phase-conjugator using nondegenerate four-wave mixing is studied, in which a strong steady-state frequency-varied phase-conjugate wave is obtained by operating the crystal at an elevated temperature. Second, wavelength-multiplexed crystal fiber holograms are investigated. The minimum channel separation is proposed to achieve maximum storage capacity. The cross-talk-limited storage capacity is evaluated. The requirement of the laser linewidth for wavelength-multiplexing applications is studied.