Fabrication and characterization of periodically poled ferroelectrics
Date Issued
2011
Date
2011
Author(s)
Pei, Shan-Chuang
Abstract
Periodically poled ferroelectric crystal fibers are expected to have advantages when using in fiber based nonlinear applications. The laser-heated pedestal growth (LHPG) method with the external electric field in-situ poling is used to fabricate periodically poled LiNbO3 (PPLN) and periodically poled LiTaO3 (PPLT) crystal fibers. In application, a novel self-cascaded first-order second-harmonic generation and third-order sum-frequency generation in a ZnO:PPLN crystal fiber was demonstrated for the generation of tunable blue–green light. The tuning range was more than 40 nm, from 471.3 to 515 nm.
To facilitate wave propagation with low loss, glass-clad LT fibers were fabricated by a co-drawing LHPG method for the first time. The glass-clad fibers are classified into two different categories by the measurements of refractive index profiles. One is a step-index fiber and the other is a graded-index fiber. Both fiber types are multimode at present, but single-mode LT fibers could be fabricated with the high-precision control of the LHPG system.
To characterize the periodically poled ferroelectrics, optical coherence tomography (OCT) technique was employed on the nonlinear medium for the first time. Using the Ce3+:YAG double-clad crystal fiber based ultrahigh resolution OCT system, the refractive index difference and uniformity of domain boundary a PPLN crystal were successfully examined.
Furthermore, it is demonstrated that the complex structure, dispersion, and small index contrast of periodically poled ferroelectric waveguides can be non-invasively characterized. An axial resolution of 0.68 μm, an transversal resolution of 3.2 μm, and an index contrast sensitivity of 4×10-7 were achieved. The index difference between the +z and –z domains in a MgO-doped congruent LiNbO3 was estimated to be 4.2×10-4, which is an important indicator for the quality of the poled ferroelectrics. The dispersion of extraordinary wave of a 5 mol.% MgO-doped CLN was characterized from 500 to 750 nm at room temperature. The high spatial resolution and high index contrast sensitivity technique can facilitate the development of quasi-phased nonlinear waveguide devices for improving wavelength conversion efficiency as well as reducing insertion loss by mode-matched coupling.
Subjects
periodically poled
ferroelectrics
optical coherence tomography
Type
thesis
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