SINGLE CRYSTAL FIBERS: GROWTH DYNAMICS AND NONLINEAR OPTICAL INTERACTIONS

Single crystal fibers (SCF) offer a combination of material properties and waveguide geometry unavailable in either glass optical fibers of bulk single crystals. The beam confinement in a waveguide structure together with the large nonlinear optical susceptibilities characteristic of crystalline media can lead to dramatic increases in the efficiency of nonlinear optical interactions. This dissertation discusses a number of theoretical and experimental results regarding the growth and optical properties of SCF.; Linear and nonlinear optical processes in SCF are modelled in the first section of the dissertation. The scattering caused by nonuniformities in the fiber are analyzed in some detail, including corrections accounting for large index of refraction differences between the core and cladding. It is shown that the diameter of SCF must be controlled to 0.1-1% for typical devices. The effects of the modal electric field distribution on the efficiency of nonlinear interactions is discussed in terms of an effective area for a set of interacting modes. It is shown that in most cases modal dispersion can be used for phasematching only at the expense of significantly reduced efficiency. Intentional modulation of the linear and nonlinear properties of the fibers to produce Bragg devices and to quasiphasematch nonlinear interactions is discussed.; The technique used to produce the SCF is laser-heated pedestal growth. The dynamic response of this process has been modelled, and the influence of various growth parameters on the stability of the process is discussed. The design and construction of a growth apparatus with novel optical and mechanical systems to ensure adequate thermal and mechanical stability is described, along with a real-time diameter measurement and control system.; Results for the growth and optical properties of SCF are presented, and shown to be in accord with theory. Scattering losses in sapphire fibers have been measured to be as low as 0.1 dB/m. The distribution of ferroelectric domains in lithium niobate fibers is discussed in terms of the thermoelectrically generated fields, and techniques for achieving uniform and periodic poling are presented. Techniques for cladding SCF are discussed with emphasis on the characterization of the highly nonlinear diffusion of protons in lithium niobate.