Toward Single-Mode Active Crystal Fibers for Next-Generation High-Power Fiber Devices

Abstract

We report what we believe to be the first demonstration of a facile approach with controlled geometry for the production of crystal-core ceramic-clad hybrid fibers for scaling fiber devices to high average powers. The process consists of dip coating a solution of polycrystalline alumina onto a high-crystallinity 40-μm-diameter Ti:sapphire single-crystalline core followed by thermal treatments. Comparison of the measured refractive index with high-resolution transmission electron microscopy reveals that a Ca/Si-rich intragranular layer is precipitated at grain boundaries by impurity segregation and liquid-phase formation due to the relief of misfit strain energy in the Al2O3 matrix, slightly perturbing the refractive index and hence the optical properties. Additionally, electron backscatter diffractions supply further evidence that the Ti:sapphire single-crystalline core provides the template for growth into a sacrificial polycrystalline cladding, bringing the core and cladding into a direct bond. The thus-prepared doped crystal core with the undoped crystal cladding was achieved through the abnormal grain-growth process. The presented results provide a general guideline both for controlling crystal growth and for the performance of hybrid materials and provides insights into how one might design single-mode high-power crystal fiber devices.

Single Crystal Fibers: Diversified Functional Crystal Material

“…The key to the sol-gel method is the preparation of the precursor and the optimization of the sintering process. In 2014, Chien-Chih Lai et al reported the cladding preparation of crystalline Al 2 O 3 on a Ti: Al 2 O 3 SCF with a diameter of 40 μm by Sol-gel method [43]. In the first step, the nanoalumina powder, ethanol and surfactant are mixed in proportion.…”

All-solid anti-resonant single crystal fibers

“…Therefore, it is common for cladding materials to have lower refractive indices and similar thermal expansion coefficients to that of the core. Effective cladding methods include the magnetron sputtering [12], Sol-Gel method [13,14], liquid phase epitaxy [15], co-drawing laser heating pedestal growth (LHPG) [16][17][18][19][20][21][22][23][24], ion implantation [25][26][27][28], and micro-structure cladding [7,29,30].…”

Ligand-Driven and Full-Color-Tunable Fiber Source: Toward Next-Generation Clinic Fiber-Endoscope Tomography with Cellular Resolution

“…Herein, we demonstrated defect-driven full-color broadband emission by engineering a glass-clad sapphire crystalline-core fiber using the laser-heated pedestal growth (LHPG) technique to create new defect levels within the bandgap and conduction band. − Glass-clad sapphire fibers with and without thermal treatment presented tunable full-color emission when pumped with 325 nm excitation. Unlike heavy particle irradiation − and thermochemical reaction, − which are often accompanied by poor crystallinity and insufficient formation of F- and F 2 -type color centers, leading to a limited bandwidth and low-yield emission, our proposed facile approach can not only provide a range extending over 50 nm deeper into the UV region than that previously achieved and efficient red emission over 600 nm but also can preserve the material’s high crystallinity.…”