Atomically smooth hybrid crystalline-core glass-clad fibers for low-loss broadband wave guiding

Abstract

We demonstrate direct evidence for the first realization of atomically smooth sapphire crystalline fiber cores with a surface variation of only ~1.9 Å. The hybrid glass-clad crystalline cores were grown by a laser-based fiber drawing technique. Because of the improvement in crystal fiber quality, we were able, for the first time, to comprehensively and quantitatively elucidate the correlation between fiber nanostructure and optical loss. We also experimentally demonstrated that high-temperature treatment has a significant impact on defect relaxation and promotes excellent crystallinity, and hence enables low-loss optical wave guiding. The experimentally measured propagation losses in the order of 0.01-0.1 dB/cm are the lowest ever reported among conventional Ti:sapphire channel waveguides and ultrafast-laser-inscribed waveguides, and agree well with the theory. Through experiments and numerical calculation, we have demonstrated that low threshold and high efficiency of Ti:sapphire crystal fiber lasers are possible with the atomic-level roughness, low-loss propagation, and high crystallinity of the Ti:sapphire crystalline core.

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

“…To our knowledge, these high conversion efficiencies are the highest among conventional glass fibers. − The high optical-to-optical conversion efficiency can be ascribed to the large emission cross-sections of the color centers produced by the odd-parity phonon vibrations . The emission cross-sections of the F- and F 2 -type color emitters in the sapphire crystal are 1–2 orders of magnitude higher than those found in typical transition-metal-doped sapphire − and YAG ,, wideband gain media (10 –23 m 2 vs 10 –21 –10 –22 m 2 ). The resulting high conversion efficiency is also the highest reported to date among the existing waveguide-type white light-production techniques, including that obtained using supercontinuum lasers.…”

Properties of waveguides filled with anisotropic metamaterials

“…Another good example of a radially structured metamaterial waveguide is a hybrid-glass metamaterial fiber, which was reported for nonlinear effects [70]. This waveguide is fabricated by a laser-based fiber drawing technique [71,72]. To fabricate such a waveguide, sapphire (α − Al 2 O 3 ) was taken as a seed dielectric core and dendrite crystalline γ − Al 2 O 3 was deposited on it.…”

Ultralow‐Threshold Continuous‐Wave Room‐Temperature Crystal‐Fiber/Nanoperovskite Hybrid Lasers for All‐Optical Photonic Integration

“…The former is better than the reported values [9] and is beneficial for an enhanced photon recycling effect, [10] while the latter minimizes undesirable scattering, thus supporting the ultralow intracavity loss required for a low-threshold CW laser. The intrinsic propagation loss was estimated to be <0.1 dB cm −1 , [11] which is sufficiently low for optical resonance in the microscale crystal-fiber cavity ( Figure S9, Supporting Information). Notably, compared to the nanoimprinted waveguides that are processed through optical lithography and have extremely large losses of 18.5 and 27.7 dB cm −1 , respectively, [5] this ≈λ/61 (≈12.5 nm/762 nm) smooth flatness ensures ultralow loss for optical resonance and low-threshold laser operation.…”