Abstract
We report the latest progress on fabrication of rare earth doped single crystal yttrium aluminum garnet (YAG) core/undoped YAG cladded fibers. Rare-earth doped single crystal core fibers were grown with laser heated pedestal growth methods. In a second step, epitaxial methods were used to grow a single crystalline undoped YAG cladding onto the core fiber. Hydrothermal and liquid phase epitaxy methods utilize the core doped fiber as the seed. X-ray diffraction of cladding reveals an equilibrium (110) morphology. Energy-dispersive X-ray spectroscopy analysis shows there is minimal diffusion of rare-earth dopants into the cladding structure. The use of scandium doping is shown to substitute at the Al3+ site, thereby allowing an additional tunability of refractive index of core structure material besides conventional Y3+ site dopants. The use of these epitaxial growth methods enables material compatibility, tuning of refractive index, and conformal growth of cladding structures onto core fibers for optical devices.
Highlights
There has been growing interest in developing high-power fiber lasers with nearly diffraction limited beam quality
For a single crystal yttrium aluminum garnet (YAG) cladding grown epitaxially, our measurements show the ratio of the measured intensities of 400 to 800 reflections are ∼1.8 in agreement with the expected value
Sc substitution shown as points, for showing aninincreased d‐spacing measured using ellipsometry changes polarization of light for gre reflected from samples using a knife-edge illumination technique
Summary
There has been growing interest in developing high-power fiber lasers with nearly diffraction limited beam quality. The lower SBS cross-section for YAG would lead to reduced non-linear effects and enable much greater potential for high peak and average laser power output [11]. A recent study suggests that based on thermal and non-linear effects, a Ho doped silica fiber would have a limit of ∼3 kW single frequency power compared to an all crystalline Ho-doped YAG fiber which could generate 35 kW of single frequency eye-safe laser power [13]. In fiber optics there has been a great deal of studies to explore doped-YAG where the dopant is Nd3+ , Er3+ , Yb3+ , or Cr4+ Due to their low thermal conductivity their applications as high power laser materials is limited [20]. We report on progress in the characterization of a scandium (Sc):YAG crystal cladding layer grown epitaxially on a YAG substrate as deposited successfully with the liquid phase epitaxy (LPE) method
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