High-efficiency and broadband tunable Raman fiber laser in a chalcogenide fiber based on the Fresnel reflection.

A high-efficiency and broadband tunable chalcogenide fiber Raman laser with the Fabry-Perot (F-P) cavity formed by the Fresnel reflection was established. A maximum average power slope efficiency of around 43% and a maximum output peak power of about 2.9 W at 2148 nm were demonstrated by using a 2 µm nanosecond pump source. The laser shows a broadened pulse width of 674 ns and a broadband tunability of the central wavelength from 2100 to 2186 nm. The Raman Fabry-Perot cavity constituted by the Fresnel reflection from chalcogenide fiber endfaces can operate at any wavelength without the aid of any additional optical feedback element. This will facilitate the realization of fiber lasers with excellent performance and compact system, especially in the mid-infrared region.

A Comparative Study on Optofluidic Fenton Microreactors Integrated with Fe-Based Materials for Water Treatment.

The catalysts employed in catalytic reactors greatly affect the reaction efficiency of the reaction system and the reactor's performance. This work presents a rapid comparative study on three kinds of Fe-based materials integrated into an optofluidic Fenton reactor for water treatment. The Fe-based sheets (FeSiB, FeNbCuSiB, and FeNi) were respectively implanted into the reaction chamber to degrade the organic dyes with the assistance of H2O2. In the experiment, by adjusting the hydrogen peroxide concentration, flow rate, and light irradiation, the applicable conditions of the Fe-based materials for the dye degradation could be evaluated quickly to explore the optimal design of the Fenton reaction system. The results indicated that FeNi (1j85) exhibits excellent degradability in the microreactor, the reaction rate can reach 23.4%/s at the flow rate of 330 µL/min, but its weak corrosion resistance was definitely demonstrated. Although the initial degradability of the microreactor by using FeNbCuSiB (1k107) was not as good as that of 1j85, it increased after being reused several times instead, and the degradation efficiency reached >98% after being reused five times. However, the FeSiB (1k101) material shows the worst degradability and recycling. Therefore, in contrast, 1k107 has the greatest potential to be used in Fenton reactors for practical water treatment.

Polyelectrolyte/Graphene Oxide Nano-Film Integrated Fiber-Optic Sensors for High-Sensitive and Rapid-Response Humidity Measurement.

Optical fiber humidity sensors have sparked enormous interests in many fields because of their excellent features. However, it remains a great challenge to balance sensitivity, humidity response, temperature crosstalk, and wet hysteresis for real-world application. To overcome this trade-off, an optical fiber humidity sensor is developed here by coating functional graphene oxide (GO)/polyelectrolyte nanocomposite film on the excessively tilted fiber grating (ex-TFG), in which GO/polyelectrolyte nanocomposite film is employed for enhancing the hydrophilicity and accelerating the adsorption/desorption of water molecule, while the ex-TFG is utilized for improving the sensitivity of refractive index and eliminating the crosstalk of temperature. By this design, optical fiber humidity sensors achieve high sensitivity, rapid response and recovery, low hysteresis, and temperature crosstalk as well as excellent repeatability and stability in large relative humidity (RH) range. Our work provides a promising platform for effective RH monitoring systems that can be widely applied in rapid diagnostics, pharmacy, precision medicine, and so forth.

A Highly Strained Phase in PbZr0.2Ti0.8O3 Films with Enhanced Ferroelectric Properties.

Although epitaxial strain imparted by lattice mismatch between a film and the underlying substrate has led to distinct structures and emergent functionalities, the discrete lattice parameters of limited substrates, combined with strain relaxations driven by film thickness, result in severe obstructions to subtly regulate electro-elastic coupling properties in perovskite ferroelectric films. Here a practical and universal method to achieve highly strained phases with large tetragonal distortions in Pb-based ferroelectric films through synergetic effects of moderately (≈1.0%) misfit strains and laser fluences during pulsed laser deposition process is demonstrated. The phase possesses unexpectedly large Poisson's ratio and negative thermal expansion, and concomitant enhancements of spontaneous polarization (≈100 µC cm-2) and Curie temperature (≈800 °C), 40% and 75% larger than that of bulk counterparts, respectively. This strategy efficiently circumvents the long-standing issue of limited numbers of discrete substrates and enables continuous regulations of exploitable lattice states in functional oxide films with tightly elastic coupled performances beyond their present levels.