Lithium niobate: Single crystal fiber growth and quasi-phase-matching

Compact laser sources in the visible region of the spectrum are needed for color projection display systems, increasing the storage capacity of optical discs, and analytical chemistry. A convenient way to produce light of the desired wavelength is to frequency-double the light from infrared laser diodes.; Lithium niobate is a nonlinear material that has been used for frequency doubling. It is relatively well-characterized, has good optical homogeneity, low loss and is readily available in large quantities. Up to now, the use of lithium niobate has been limited due to its susceptibility to photorefractive damage, and its inability to phase-match wavelengths shorter than one micron. This thesis reports on progress in lithium niobate that overcomes previous limitations by periodic poled crystals and lithium in-diffused stoichiometric crystals.; Periodically poled lithium niobate overcomes the limitations of conventionally phase-matched materials. Periodically poled crystals were grown with the laser heated pedestal growth method with different periods to generate light covering the whole visible spectrum. The chosen fiber geometry enables the use of the largest nonlinear coefficient, d{dollar}sb{lcub}33{rcub}{dollar}, yielding high conversion efficiencies. For example, using 4.25 W of infrared light at 1.064 {dollar}mu{dollar}m, 2 W of green light was generated in a sample 1.3 mm long.; The influence of stoichiometry on the refractive index of LiNbO{dollar}sb3{dollar} was studied. A technique to manufacture lithium-rich crystals was used to produce high quality nonlinear crystals. To study this process, the stoichiometry-dependence of the lithium self-diffusion constant was measured. The refractive indices of the resulting lithium-rich LiNbO{dollar}sb3{dollar} were determined and high efficiency frequency doubling generating 1.6 W of 533 nm radiation was demonstrated in such a crystal.; The dynamics of the crystal diameter during the laser heated pedestal growth were studied. The influence of noise such as heating laser fluctuations or noise in the translator speeds on the diameter and quality of the fibers was investigated. The models developed to describe the dynamics of the molten zone during growth show good qualitative agreement with the observed data.